Fix lint issues

securesystemslib/ecdsa_keys.py

@@ -327,15 +327,11 @@ def verify_signature(public_key, scheme, signature, data):
             f"Failed to load PEM key {public_key}"
         ) from e
 
-    if not isinstance(  # pylint: disable=no-else-raise
-        ecdsa_key, ec.EllipticCurvePublicKey
-    ):
+    if not isinstance(ecdsa_key, ec.EllipticCurvePublicKey):
         raise exceptions.FormatError(
             "Invalid ECDSA public" " key: " + repr(public_key)
         )
-
-    else:
-        logger.debug("Loaded a valid ECDSA public key.")
+    logger.debug("Loaded a valid ECDSA public key.")
 
     # verify() raises an 'InvalidSignature' exception if 'signature'
     # is invalid.

securesystemslib/exceptions.py

@@ -21,20 +21,14 @@
 class Error(Exception):
     """Indicate a generic error."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class Warning(Warning):  # pylint: disable=redefined-builtin
     """Generic warning.  It is used by the 'warnings' module."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class FormatError(Error):
     """Indicate an error while validating an object's format."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class InvalidMetadataJSONError(FormatError):
     """Indicate that a metadata file is not valid JSON."""
@@ -51,8 +45,6 @@ def __str__(self):
 class UnsupportedAlgorithmError(Error):
     """Indicate an error while trying to identify a user-specified algorithm."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class BadHashError(Error):
     """Indicate an error while checking the value a hash object."""
@@ -76,14 +68,10 @@ def __str__(self):
 class BadPasswordError(Error):
     """Indicate an error after encountering an invalid password."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class CryptoError(Error):
     """Indicate any cryptography-related errors."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class BadSignatureError(CryptoError):
     """Indicate that some metadata has a bad signature."""
@@ -100,45 +88,31 @@ def __str__(self):
 class UnknownMethodError(CryptoError):
     """Indicate that a user-specified cryptograpthic method is unknown."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class UnsupportedLibraryError(Error):
     """Indicate that a supported library could not be located or imported."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class InvalidNameError(Error):
     """Indicate an error while trying to validate any type of named object."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class NotFoundError(Error):
     """If a required configuration or resource is not found."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class URLMatchesNoPatternError(Error):
     """If a URL does not match a user-specified regular expression."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class InvalidConfigurationError(Error):
     """If a configuration object does not match the expected format."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class StorageError(Error):
     """Indicate an error occured during interaction with an abstracted storage
     backend."""
 
-    pass  # pylint: disable=unnecessary-pass
-
 
 class UnverifiedSignatureError(Error):
     """Signature could not be verified: either signature was incorrect or

securesystemslib/gpg/common.py

@@ -210,7 +210,7 @@ def parse_pubkey_bundle(data):
             # - there must be least one User ID packet, or
             # - order and type of signatures, or
             # - disallow duplicate packets
-            if (  # pylint: disable=no-else-raise
+            if (
                 packet_type != PACKET_TYPE_PRIMARY_KEY
                 and not key_bundle[PACKET_TYPE_PRIMARY_KEY]["key"]
             ):
@@ -219,7 +219,7 @@ def parse_pubkey_bundle(data):
                     "got '{}'.".format(PACKET_TYPE_PRIMARY_KEY, packet_type)
                 )
 
-            elif (
+            if (
                 packet_type == PACKET_TYPE_PRIMARY_KEY
                 and key_bundle[PACKET_TYPE_PRIMARY_KEY]["key"]
             ):
@@ -228,7 +228,7 @@ def parse_pubkey_bundle(data):
             # Fully parse master key to fail early, e.g. if key is malformed
             # or not supported, but also retain original packet for subkey binding
             # signature verification
-            elif packet_type == PACKET_TYPE_PRIMARY_KEY:
+            if packet_type == PACKET_TYPE_PRIMARY_KEY:
                 key_bundle[PACKET_TYPE_PRIMARY_KEY] = {
                     "key": parse_pubkey_payload(bytearray(payload)),
                     "packet": packet,

securesystemslib/keys.py

@@ -454,24 +454,21 @@ def format_keyval_to_metadata(keytype, scheme, key_value, private=False):
         # key in the returned dictionary, ensure the private key is actually
         # present in 'key_val' (a private key is optional for 'KEYVAL_SCHEMA'
         # dicts).
-        if "private" not in key_value:  # pylint: disable=no-else-raise
+        if "private" not in key_value:
             raise exceptions.FormatError(
-                "The required private key"
-                " is missing from: " + repr(key_value)
+                "The required private key is missing from: " + repr(key_value)
             )
 
-        else:
-            return {"keytype": keytype, "scheme": scheme, "keyval": key_value}
+        return {"keytype": keytype, "scheme": scheme, "keyval": key_value}
 
-    else:
-        public_key_value = {"public": key_value["public"]}
+    public_key_value = {"public": key_value["public"]}
 
-        return {
-            "keytype": keytype,
-            "scheme": scheme,
-            "keyid_hash_algorithms": settings.HASH_ALGORITHMS,
-            "keyval": public_key_value,
-        }
+    return {
+        "keytype": keytype,
+        "scheme": scheme,
+        "keyid_hash_algorithms": settings.HASH_ALGORITHMS,
+        "keyval": public_key_value,
+    }
 
 
 def format_metadata_to_key(
@@ -830,15 +827,14 @@ def verify_signature(
 
     # Verify that the KEYID in 'key_dict' matches the KEYID listed in the
     # 'signature'.
-    if key_dict["keyid"] != signature["keyid"]:  # pylint: disable=no-else-raise
+    if key_dict["keyid"] != signature["keyid"]:
         raise exceptions.CryptoError(
             "The KEYID ("
             " " + repr(key_dict["keyid"]) + " ) in the given key does not match"
             " the KEYID ( " + repr(signature["keyid"]) + " ) in the signature."
         )
 
-    else:
-        logger.debug("The KEYIDs of key_dict and the signature match.")
+    logger.debug("The KEYIDs of key_dict and the signature match.")
 
     # Using the public key belonging to 'key_dict'
     # (i.e., rsakey_dict['keyval']['public']), verify whether 'signature'
@@ -1235,42 +1231,40 @@ def extract_pem(pem, private_pem=False):
 
     except ValueError:
         # Be careful not to print private key material in exception message.
-        if not private_pem:  # pylint: disable=no-else-raise
-            raise exceptions.FormatError(  # pylint: disable=raise-missing-from
-                "Required PEM"
-                " header " + repr(pem_header) + "\n not found in PEM"
-                " string: " + repr(pem)
-            )
-
-        else:
+        if not private_pem:
             raise exceptions.FormatError(  # pylint: disable=raise-missing-from
-                "Required PEM"
-                " header "
+                "Required PEM header "
                 + repr(pem_header)
-                + "\n not found in private PEM string."
+                + "\n not found in PEM string: "
+                + repr(pem)
             )
 
+        raise exceptions.FormatError(  # pylint: disable=raise-missing-from
+            "Required PEM header "
+            + repr(pem_header)
+            + "\n not found in private PEM string."
+        )
+
     try:
         # Search for 'pem_footer' after the PEM header.
         footer_start = pem.index(pem_footer, header_start + len(pem_header))
 
     except ValueError:
         # Be careful not to print private key material in exception message.
-        if not private_pem:  # pylint: disable=no-else-raise
+        if not private_pem:
             raise exceptions.FormatError(  # pylint: disable=raise-missing-from
-                "Required PEM"
-                " footer " + repr(pem_footer) + "\n not found in PEM"
-                " string " + repr(pem)
-            )
-
-        else:
-            raise exceptions.FormatError(  # pylint: disable=raise-missing-from
-                "Required PEM"
-                " footer "
+                "Required PEM footer "
                 + repr(pem_footer)
-                + "\n not found in private PEM string."
+                + "\n not found in PEM string "
+                + repr(pem)
             )
 
+        raise exceptions.FormatError(  # pylint: disable=raise-missing-from
+            "Required PEM footer "
+            + repr(pem_footer)
+            + "\n not found in private PEM string."
+        )
+
     # Extract only the public portion of 'pem'.  Leading or trailing whitespace
     # is excluded.
     pem = pem[header_start : footer_start + len(pem_footer)]

securesystemslib/rsa_keys.py

@@ -1069,11 +1069,7 @@ def _decrypt(file_contents, password):
     # specified so that the expected derived key is regenerated correctly.
     # Discard the old "salt" and "iterations" values, as we only need the old
     # derived key.
-    (
-        junk_old_salt,  # pylint: disable=unused-variable
-        junk_old_iterations,  # pylint: disable=unused-variable
-        symmetric_key,
-    ) = _generate_derived_key(password, salt, iterations)
+    _, _, symmetric_key = _generate_derived_key(password, salt, iterations)
 
     # Verify the hmac to ensure the ciphertext is valid and has not been altered.
     # See the encryption routine for why we use the encrypt-then-MAC approach.

securesystemslib/schema.py

@@ -597,16 +597,14 @@ def __init__(self, lo=-2147483648, hi=2147483647):
         self._hi = hi
 
     def check_match(self, object):  # pylint: disable=redefined-builtin
-        if isinstance(  # pylint: disable=no-else-raise
-            object, bool
-        ) or not isinstance(object, int):
+        if isinstance(object, bool) or not isinstance(object, int):
             # We need to check for bool as a special case, since bool
             # is for historical reasons a subtype of int.
             raise exceptions.FormatError(
                 "Got " + repr(object) + " instead of an integer."
             )
 
-        elif not (self._lo <= object <= self._hi):
+        if not (self._lo <= object <= self._hi):
             int_range = "[" + repr(self._lo) + ", " + repr(self._hi) + "]."
             raise exceptions.FormatError(
                 repr(object) + " not in range " + int_range
@@ -748,7 +746,7 @@ def __init__(self, object_name="object", **required):
         """
 
         # Ensure valid arguments.
-        for key, schema in required.items():  # pylint: disable=unused-variable
+        for schema in required.values():
             if not isinstance(schema, Schema):
                 raise exceptions.FormatError(
                     "Expected Schema but" " got " + repr(schema)
@@ -886,22 +884,20 @@ def __init__(
         self._struct_name = struct_name
 
     def check_match(self, object):  # pylint: disable=redefined-builtin
-        if not isinstance(  # pylint: disable=no-else-raise
-            object, (list, tuple)
-        ):
+        if not isinstance(object, (list, tuple)):
             raise exceptions.FormatError(
                 "Expected "
                 + repr(self._struct_name)
                 + "; but got "
                 + repr(object)
             )
 
-        elif len(object) < self._min:
+        if len(object) < self._min:
             raise exceptions.FormatError(
                 "Too few fields in " + self._struct_name
             )
 
-        elif len(object) > len(self._sub_schemas) and not self._allow_more:
+        if len(object) > len(self._sub_schemas) and not self._allow_more:
             raise exceptions.FormatError(
                 "Too many fields in " + self._struct_name
             )

securesystemslib/unittest_toolbox.py

@@ -120,7 +120,7 @@ def random_path(self, length=7):
         """Generate a 'random' path consisting of random n-length strings."""
 
         rand_path = "/" + self.random_string(length)
-        for i in range(2):  # pylint: disable=unused-variable
+        for _ in range(2):
             rand_path = os.path.join(rand_path, self.random_string(length))
 
         return rand_path
@@ -130,7 +130,7 @@ def random_string(length=15):
         """Generate a random string of specified length."""
 
         rand_str = ""
-        for letter in range(length):  # pylint: disable=unused-variable
+        for _ in range(length):
             rand_str += random.choice("abcdefABCDEF" + string.digits)  # nosec
 
         return rand_str

securesystemslib/util.py

@@ -450,10 +450,8 @@ def digests_are_equal(digest1: str, digest2: str) -> bool:
 
     are_equal = True
 
-    for element in range(  # pylint: disable=consider-using-enumerate
-        len(digest1)
-    ):
-        if digest1[element] != digest2[element]:
+    for val1, val2 in zip(digest1, digest2):
+        if val1 != val2:
             are_equal = False
 
     return are_equal

tests/check_public_interfaces.py

@@ -29,18 +29,11 @@
   when explicitly invoked.
 """
 
-import inspect  # pylint: disable=unused-import
-import json  # pylint: disable=unused-import
 import os
 import shutil
-import sys
 import tempfile
 import unittest
-
-if sys.version_info >= (3, 3):
-    import unittest.mock as mock  # pylint: disable=consider-using-from-import
-else:
-    import mock
+from unittest import mock
 
 import securesystemslib.exceptions  # pylint: disable=wrong-import-position
 import securesystemslib.gpg.constants  # pylint: disable=wrong-import-position

tests/test_ecdsa_keys.py

@@ -17,7 +17,6 @@
   Test cases for test_ecdsa_keys.py.
 """
 
-import os  # pylint: disable=unused-import
 import unittest
 
 import securesystemslib.ecdsa_keys
@@ -153,10 +152,7 @@ def test_verify_signature(self):
 
         # Generate an RSA key so that we can verify that non-ECDSA keys are
         # rejected.
-        (
-            rsa_pem,
-            junk,  # pylint: disable=unused-variable
-        ) = securesystemslib.rsa_keys.generate_rsa_public_and_private()
+        rsa_pem, _ = securesystemslib.rsa_keys.generate_rsa_public_and_private()
 
         # Verify that a non-ECDSA key (via the PEM argument) is rejected.
         self.assertRaises(