Add a test that exercises the GCS Credentials class

We subclass the GCS Credentials class.  We can't completely test
it without either hitting the live Google cloud or substantial
mocking, but we should be able to exercise most of the functionality
we typically use.  Do that by asking it to load a token from disk
and assert that it adds that token to a fake request headers
dictionary.

This also corrects a "problem" detected by the test.  The current
super() call uses the python3 form, which is fine in that all current
uses of this code are using python3, but we still run python27 tests
on this repo, so we'll use the python2/python3 compat syntax.

Change-Id: Ifa4209617f4be52008b6294ebd10f0deb9bd6a51

roles/upload-logs-gcs/library/test-fixtures/auth.json

@@ -0,0 +1 @@
+{"access_token": "something", "expires_in": 3599, "token_type": "Bearer"}

roles/upload-logs-gcs/library/test_zuul_google_storage_upload.py

@@ -26,6 +26,7 @@ import fixtures
 
 from bs4 import BeautifulSoup
 from .zuul_google_storage_upload import FileList, Indexer, FileDetail
+from .zuul_google_storage_upload import Credentials
 
 
 FIXTURE_DIR = os.path.join(os.path.dirname(__file__),
@@ -404,3 +405,13 @@ class TestFileDetail(testtools.TestCase):
 
         self.assertEqual(time.gmtime(0), file_detail.last_modified)
         self.assertEqual(0, file_detail.size)
+
+
+class TestCredential(testtools.TestCase):
+
+    def test_credential(self):
+        path = os.path.join(FIXTURE_DIR, 'auth.json')
+        headers = {}
+        c = Credentials(path)
+        c.before_request(None, None, None, headers)
+        self.assertEqual("Bearer something", headers['authorization'])

roles/upload-logs-gcs/library/zuul_google_storage_upload.py

@@ -260,7 +260,7 @@ def sizeof_fmt(num, suffix='B'):
 
 class Credentials(gce_cred.Credentials):
     def __init__(self, path):
-        super().__init__()
+        super(Credentials, self).__init__()
         self._path = path
         self.refresh(None)