fix: cosign chaged error code

Cosign changed its error code for non existant images and missing signatures in transparency logs, resulting connaisseur in throwing wrong errors as well. This has been fixed.

connaisseur/validators/cosign/cosign_validator.py

@@ -197,7 +197,7 @@ def __get_cosign_validated_digests(self, image: str, trust_root: dict):
                 trust_root=trust_root["name"],
             )
         elif (
-            "Error: no matching signatures:\nsignature not found in transparency log\n"
+            "Error: no matching signatures:\nsearching log query:"
             in stderr
         ):
             msg = "Failed to find signature in transparency log."
@@ -217,7 +217,7 @@ def __get_cosign_validated_digests(self, image: str, trust_root: dict):
                 image=str(image),
                 trust_root=trust_root["name"],
             )
-        elif "Error: entity not found in registry\nmain.go:" in stderr:
+        elif "MANIFEST_UNKNOWN" in stderr:
             msg = 'Image "{image}" does not exist.'
             raise NotFoundException(
                 message=msg,

tests/data/cosign/does_not_exist.txt

@@ -1,2 +1,2 @@
-Error: entity not found in registry
-main.go:46: error during command execution: entity not found in registry
+Error: GET https://index.docker.io/v2/library/testimage/manifests/v1: MANIFEST_UNKNOWN: manifest unknown; unknown tag=v1
+main.go:62: error during command execution: GET https://index.docker.io/v2/library/testimage/manifests/v1: MANIFEST_UNKNOWN: manifest unknown; unknown tag=v1

tests/data/cosign/notfound_in_tl.txt

@@ -1,2 +1,2 @@
 Error: no matching signatures:
-signature not found in transparency log
+searching log query: