credentials: eliminate distutils deprecation warnings (#3028)

While removing any usage of the deprecated `distutils` package,
("The distutils package is deprecated and slated for removal in Python 3.12.")
this internal utility can be removed straightaway because the
`shutil.which` replacement for `distutils.spawn.find_executable`
already honors the `PATHEXT` environment variable in windows systems.

See https://docs.python.org/3/library/shutil.html#shutil.which

Signed-off-by: Daniel Möller <n1ngu@riseup.net>

docker/credentials/store.py

@@ -1,11 +1,11 @@
 import errno
 import json
+import shutil
 import subprocess
 
 from . import constants
 from . import errors
 from .utils import create_environment_dict
-from .utils import find_executable
 
 
 class Store:
@@ -15,7 +15,7 @@ class Store:
             and erasing credentials using `program`.
         """
         self.program = constants.PROGRAM_PREFIX + program
-        self.exe = find_executable(self.program)
+        self.exe = shutil.which(self.program)
         self.environment = environment
         if self.exe is None:
             raise errors.InitializationError(

docker/credentials/utils.py

@@ -1,32 +1,4 @@
-import distutils.spawn
 import os
-import sys
-
-
-def find_executable(executable, path=None):
-    """
-    As distutils.spawn.find_executable, but on Windows, look up
-    every extension declared in PATHEXT instead of just `.exe`
-    """
-    if sys.platform != 'win32':
-        return distutils.spawn.find_executable(executable, path)
-
-    if path is None:
-        path = os.environ['PATH']
-
-    paths = path.split(os.pathsep)
-    extensions = os.environ.get('PATHEXT', '.exe').split(os.pathsep)
-    base, ext = os.path.splitext(executable)
-
-    if not os.path.isfile(executable):
-        for p in paths:
-            for ext in extensions:
-                f = os.path.join(p, base + ext)
-                if os.path.isfile(f):
-                    return f
-        return None
-    else:
-        return executable
 
 
 def create_environment_dict(overrides):

tests/integration/credentials/store_test.py

@@ -1,9 +1,9 @@
 import os
 import random
+import shutil
 import sys
 
 import pytest
-from distutils.spawn import find_executable
 
 from docker.credentials import (
     CredentialsNotFound, Store, StoreError, DEFAULT_LINUX_STORE,
@@ -22,9 +22,9 @@ class TestStore:
     def setup_method(self):
         self.tmp_keys = []
         if sys.platform.startswith('linux'):
-            if find_executable('docker-credential-' + DEFAULT_LINUX_STORE):
+            if shutil.which('docker-credential-' + DEFAULT_LINUX_STORE):
                 self.store = Store(DEFAULT_LINUX_STORE)
-            elif find_executable('docker-credential-pass'):
+            elif shutil.which('docker-credential-pass'):
                 self.store = Store('pass')
             else:
                 raise Exception('No supported docker-credential store in PATH')