Fix bug in git_credentials()

git_credentials() was converting the stdin argument to bytes. However
according to the Python3 documentation subprocess.communicate() expects
a string when universal_newlines=True is passed to Popen.

The symptom was that git review would fail in p.communicate(stdin) on
line 156 with the message "'bytes' object has no attribute 'encode'".
This was observed with Python version 3.6.9 when running git-review
against a gerrit repo over https, where the repo requires username and
password to authenticate.

Change-Id: I0c0314c3f7b0eb631e72e4ac187a9d443a2bc82b

git_review/cmd.py

@@ -171,7 +171,7 @@ def git_credentials(url):
     """Return credentials using git credential or None."""
     cmd = 'git', 'credential', 'fill'
     stdin = 'url=%s' % url
-    rc, out = run_command_status(*cmd, stdin=stdin.encode('utf-8'))
+    rc, out = run_command_status(*cmd, stdin=stdin)
     if rc:
         return None
     data = dict(line.split('=', 1) for line in out.splitlines())

git_review/tests/test_unit.py

@@ -305,7 +305,7 @@ class GitReviewUnitTest(testtools.TestCase):
         # This gets encoded to utf8 which means the type passed down
         # is bytes.
         mock_run.assert_called_once_with('git', 'credential', 'fill',
-                                         stdin=b'url=%s' % url.encode('utf-8'))
+                                         stdin='url=%s' % url)
         calls = [mock.call(url), mock.call(url, auth=('user', 'pass'))]
         mock_get.assert_has_calls(calls)
 
@@ -323,7 +323,7 @@ class GitReviewUnitTest(testtools.TestCase):
         # This gets encoded to utf8 which means the type passed down
         # is bytes.
         mock_run.assert_called_once_with('git', 'credential', 'fill',
-                                         stdin=b'url=%s' % url.encode('utf-8'))
+                                         stdin='url=%s' % url)
         calls = [mock.call(url), mock.call(url, auth=('user', 'pass'))]
         mock_get.assert_has_calls(calls)
 
@@ -341,7 +341,7 @@ class GitReviewUnitTest(testtools.TestCase):
         # This gets encoded to utf8 which means the type passed down
         # is bytes.
         mock_run.assert_called_once_with('git', 'credential', 'fill',
-                                         stdin=b'url=%s' % url.encode('utf-8'))
+                                         stdin='url=%s' % url)
         mock_get.assert_called_once_with(url)
 
     @mock.patch('sys.argv', ['argv0', '--track', 'branch'])

test-requirements.txt

@@ -1,5 +1,5 @@
 hacking>=2.0.0,<2.1.0
 mock
 fixtures>=0.3.14
-stestr>=2.2.0
+stestr>=2.2.0,<3.0.0
 testtools>=0.9.34