Fix hook test on Windows

This test was failing on Windows, for several reasons. Number one, the paths
for the hook test were hard-coded with forward slashes as path separators. I
replaced those with calls to os.path.join. Number two, the drive letter was
getting in the way of the path manipulation. On Windows, I'm using
os.path.splitdrive to fix that.

CONTRIBUTORS.txt

@@ -21,3 +21,4 @@ Contributors (by order of appearance) :
 - Florent Xicluna
 - Austin Morton
 - Michael McNeil Forbes
+- Christian Long

flake8/tests/test_hooks.py

@@ -8,6 +8,7 @@ except ImportError:
     import mock
 
 import flake8.hooks
+from flake8.util import is_windows
 
 
 def excluded(filename):
@@ -15,24 +16,43 @@ def excluded(filename):
 
 
 class TestGitHook(unittest.TestCase):
+    if is_windows:
+        current_drive, ignore_tail = os.path.splitdrive(os.getcwd())
+        fake_path_at_root_of_filesystem = os.path.join(current_drive,
+                                                       os.path.sep,
+                                                       'fake',
+                                                       'tmp')
+    else:
+        fake_path_at_root_of_filesystem = os.path.join(os.path.sep,
+                                                       'fake',
+                                                       'tmp')
+
     @mock.patch('os.makedirs')
     @mock.patch('flake8.hooks.open', create=True)
     @mock.patch('shutil.rmtree')
-    @mock.patch('tempfile.mkdtemp', return_value='/fake/tmp')
+    @mock.patch('tempfile.mkdtemp',
+                return_value=fake_path_at_root_of_filesystem)
     @mock.patch('flake8.hooks.run',
-                return_value=(None, ['foo/afile.py', 'foo/bfile.py'], None))
+                return_value=(None,
+                              [os.path.join('foo', 'afile.py'),
+                               os.path.join('foo', 'bfile.py')],
+                              None))
     @mock.patch('flake8.hooks.get_style_guide')
     def test_prepends_tmp_directory_to_exclude(self, get_style_guide, run,
                                                *args):
         style_guide = get_style_guide.return_value = mock.Mock()
-        style_guide.options.exclude = ['foo/afile.py']
-        style_guide.options.filename = ['foo/*']
+        style_guide.options.exclude = [os.path.join('foo', 'afile.py')]
+        style_guide.options.filename = [os.path.join('foo', '*')]
         style_guide.excluded = excluded
 
         flake8.hooks.git_hook()
 
-        dirname, filename = os.path.split(os.path.abspath('foo/bfile.py'))
-        tmpdir = os.path.join('/fake/tmp', dirname[1:])
+        dirname, filename = os.path.split(
+            os.path.abspath(os.path.join('foo', 'bfile.py')))
+        if is_windows:
+            ignore_drive, dirname = os.path.splitdrive(dirname)
+        tmpdir = os.path.join(self.fake_path_at_root_of_filesystem,
+                              dirname[1:])
         tmpfile = os.path.join(tmpdir, 'bfile.py')
         style_guide.check_files.assert_called_once_with([tmpfile])