Only run proxy_command unit tests when nc is available

tests/test_connection.py

@@ -25,7 +25,6 @@
 import os
 from pathlib import Path
 import socket
-import subprocess
 import sys
 import unittest
 from unittest.mock import patch
@@ -51,17 +50,10 @@
 
 from .server import Server, ServerTestCase
 
-from .util import asynctest, gss_available, patch_gss, run
+from .util import asynctest, gss_available, nc_available, patch_gss
 from .util import patch_getnameinfo, x509_available
 
 
-try:
-    run('which nc')
-    _nc_available = True
-except subprocess.CalledProcessError: # pragma: no cover
-    _nc_available = False
-
-
 class _CheckAlgsClientConnection(asyncssh.SSHClientConnection):
     """Test specification of encryption algorithms"""
 
@@ -609,7 +601,7 @@ async def test_get_server_host_key_connect_failure(self):
         with self.assertRaises(OSError):
             await asyncssh.get_server_host_key('\xff')
 
-    @unittest.skipUnless(_nc_available, 'Netcat not available')
+    @unittest.skipUnless(nc_available, 'Netcat not available')
     @asynctest
     async def test_get_server_host_key_proxy(self):
         """Test retrieving a server host key using proxy command"""
@@ -621,7 +613,7 @@ async def test_get_server_host_key_proxy(self):
 
         self.assertEqual(key, keylist[0])
 
-    @unittest.skipUnless(_nc_available, 'Netcat not available')
+    @unittest.skipUnless(nc_available, 'Netcat not available')
     @asynctest
     async def test_get_server_host_key_proxy_failure(self):
         """Test failure retrieving a server host key using proxy command"""
@@ -1624,7 +1616,7 @@ async def test_run_server(self):
         async with self.run_server(sock):
             pass
 
-    @unittest.skipUnless(_nc_available, 'Netcat not available')
+    @unittest.skipUnless(nc_available, 'Netcat not available')
     @asynctest
     async def test_connect_reverse_proxy(self):
         """Test reverse direction SSH connection with proxy command"""

tests/test_connection_auth.py

@@ -34,7 +34,7 @@
 from .keysign_stub import create_subprocess_exec_stub
 from .server import Server, ServerTestCase
 from .util import asynctest, gss_available, patch_getnameinfo, patch_gss
-from .util import make_certificate, x509_available
+from .util import make_certificate, nc_available, x509_available
 
 
 class _FailValidateHostSSHServerConnection(asyncssh.SSHServerConnection):
@@ -658,6 +658,7 @@ async def test_get_server_auth_methods(self):
 
         self.assertEqual(auth_methods, ['hostbased'])
 
+    @unittest.skipUnless(nc_available, 'Netcat not available')
     @asynctest
     async def test_get_server_auth_methods_no_sockname(self):
         """Test getting auth methods from the test server"""

tests/util.py

@@ -24,6 +24,7 @@
 import binascii
 import functools
 import os
+import shutil
 import subprocess
 import sys
 import tempfile
@@ -33,14 +34,23 @@
 
 from cryptography.hazmat.backends.openssl import backend
 
-# pylint: disable=unused-import
+from asyncssh.gss import gss_available
+from asyncssh.logging import logger
+from asyncssh.misc import ConnectionLost, SignalReceived
+from asyncssh.packet import Byte, String, UInt32, UInt64
+from asyncssh.public_key import generate_private_key
+
+
+# pylint: disable=ungrouped-imports, unused-import
 
 try:
     import bcrypt
     bcrypt_available = hasattr(bcrypt, 'kdf')
 except ImportError: # pragma: no cover
     bcrypt_available = False
 
+nc_available = bool(shutil.which('nc'))
+
 try:
     import uvloop
     uvloop_available = True
@@ -53,14 +63,7 @@
 except ImportError: # pragma: no cover
     x509_available = False
 
-# pylint: enable=unused-import
-
-from asyncssh.gss import gss_available
-from asyncssh.logging import logger
-from asyncssh.misc import ConnectionLost, SignalReceived
-from asyncssh.packet import Byte, String, UInt32, UInt64
-from asyncssh.public_key import generate_private_key
-
+# pylint: enable=ungrouped-imports, unused-import
 
 # pylint: disable=no-member