Fix rmtree_errorhandler to skip non-existing dirs

Fixes pypa#4910.

src/pip/_internal/utils/misc.py

@@ -181,8 +181,14 @@ def rmtree_errorhandler(func, path, exc_info):
     """On Windows, the files in .svn are read-only, so when rmtree() tries to
     remove them, an exception is thrown.  We catch that here, remove the
     read-only attribute, and hopefully continue without problems."""
+    try:
+        is_readonly = os.stat(path).st_mode & stat.S_IREAD
+    except (IOError, OSError):
+        # Since the path already removed we don't raise the error
+        return
+
     # if file type currently read only
-    if os.stat(path).st_mode & stat.S_IREAD:
+    if is_readonly:
         # convert to read/write
         os.chmod(path, stat.S_IWRITE)
         # use the original function to repeat the operation

tests/unit/test_utils.py

@@ -59,6 +59,7 @@
     redact_netloc,
     remove_auth_from_url,
     rmtree,
+    rmtree_errorhandler,
     split_auth_from_netloc,
     split_auth_netloc_from_url,
     untar_file,
@@ -386,6 +387,61 @@ def test_unpack_zip(self, data):
         self.confirm_files()
 
 
+def test_rmtree_errorhandler_not_existing_directory(tmpdir):
+    """
+    Test `rmtree_errorhandler` ignores the given non-existing directory.
+    """
+    not_existing_path = str(tmpdir / 'foo')
+    func_mock = Mock()
+    rmtree_errorhandler(func_mock, not_existing_path, None)
+    func_mock.assert_not_called()
+
+
+def test_rmtree_errorhandler_readonly_directory(tmpdir):
+    """
+    Test `rmtree_errorhandler` makes the given read-only directory writable.
+    """
+    # Create read only directory
+    path = str((tmpdir / 'foo').mkdir())
+    os.chmod(path, stat.S_IREAD)
+
+    # Make sure func_mock is called with the given path
+    func_mock = Mock()
+    rmtree_errorhandler(func_mock, path, None)
+    func_mock.assert_called_with(path)
+
+    # Make sure the path is became writable
+    assert os.stat(path).st_mode & stat.S_IWRITE
+
+
+def test_rmtree_errorhandler_reraises_error(tmpdir):
+    """
+    Test `rmtree_errorhandler` re-raises an error
+    by the given non-readonly directory.
+    """
+    # Create write only directory
+    path = str((tmpdir / 'foo').mkdir())
+    os.chmod(path, stat.S_IWRITE)
+
+    # Make sure the handler re-raises an exception.
+    # Note that the raise statement without expression and
+    # active exception in the current scope throws
+    # the RuntimeError on python3 and the TypeError on python2.
+    func_mock = Mock()
+    with pytest.raises((RuntimeError, TypeError)):
+        rmtree_errorhandler(func_mock, path, None)
+
+    func_mock.assert_not_called()
+
+
+def test_rmtree_skips_not_existing_directory():
+    """
+    Test wrapped `rmtree` doesn't raise an error
+    by the given non-existing directory.
+    """
+    rmtree.__wrapped__('foo')
+
+
 class Failer:
     def __init__(self, duration=1):
         self.succeed_after = time.time() + duration