Retry queries for commits

When a pull_request event arrives we also get the commit statuses
which are attached to the commit object. Sometimes the commit is not
yet queryable and we get a 404 [1]. In this case we need to retry the
query. In the future we probably want to use that as a feedback
mechanism of a dynamic event delay.

[1] Trace
2018-06-13 11:49:11,881 ERROR zuul.GithubEventConnector: Exception moving GitHub event:
Traceback (most recent call last):
  File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 391, in run
    self._handleEvent()
  File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 226, in _handleEvent
    refresh=True)
  File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 751, in _getChange
    self._updateChange(change)
  File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 837, in _updateChange
    change.patchset)
  File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 1226, in _get_statuses
    for status in self.getCommitStatuses(project.name, sha):
  File "/usr/lib/python3.6/site-packages/zuul/driver/github/githubconnection.py", line 1171, in getCommitStatuses
    commit = repository.commit(sha)
  File "/usr/lib/python3.6/site-packages/github3/repos/repo.py", line 342, in commit
    json = self._json(self._get(url), 200)
  File "/usr/lib/python3.6/site-packages/github3/models.py", line 156, in _json
    raise exceptions.error_for(response)
github3.exceptions.NotFoundError: 404 Not Found

Change-Id: I5cc6d95ed18148657d9e5a8d132a8e43f385771d

1 files changed, 23 insertions, 0 deletions

diff --git a/tests/fakegithub.py b/tests/fakegithub.py
index 6b951ef51..df34c694b 100644
--- a/tests/fakegithub.py
+++ b/tests/fakegithub.py
@@ -14,6 +14,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import github3.exceptions
 import re
 
 FAKE_BASE_URL = 'https://example.com/api/v3/'
@@ -82,6 +83,9 @@ class FakeRepository(object):
         self.data = data
         self.name = name
 
+        # fail the next commit requests with 404
+        self.fail_not_found = 0
+
     def branches(self, protected=False):
         if protected:
             # simulate there is no protected branch
@@ -121,6 +125,25 @@ class FakeRepository(object):
         commit.set_status(state, url, description, context, user)
 
     def commit(self, sha):
+
+        if self.fail_not_found > 0:
+            self.fail_not_found -= 1
+
+            class Response:
+                status_code = 0
+                message = ''
+
+                def json(self):
+                    return {
+                        'message': self.message
+                    }
+
+            resp = Response()
+            resp.status_code = 404
+            resp.message = 'Not Found'
+
+            raise github3.exceptions.NotFoundError(resp)
+
         commit = self._commits.get(sha, None)
         if commit is None:
             commit = FakeCommit(sha)