image-download: tests to catch stray output

Add unit tests to ensure that any stray output (eg print
statements) during image-download cause a test failure.

Regression test for bug 1488914.

Change-Id: Ic19ba5693d059bf7c283702e7c333672a878a1a1
Partial-bug: 1488914

glanceclient/tests/utils.py

@@ -117,6 +117,10 @@ class FakeResponse(object):
         self.raw = RawRequest(headers, body=body, reason=reason,
                               version=version, status=status_code)
 
+    @property
+    def status(self):
+        return self.status_code
+
     @property
     def ok(self):
         return (self.status_code < 400 or
@@ -151,6 +155,9 @@ class FakeResponse(object):
                 break
             yield chunk
 
+    def release_conn(self, **kwargs):
+        pass
+
 
 class TestCase(testtools.TestCase):
     TEST_REQUEST_BASE = {