[ci] better errors on bad github response

Not sure what was wrong, but CI was getting 422s from GitHub. Using a
`raise_for_status=True` ClientSession circumvented gidgethubs native
error handling logic smothering the HTTP response body where github
places critical debugging information. Aiohttp is aware that
`raise_for_status` provides no access to the response body. They addressed
this in https://github.com/aio-libs/aiohttp/pulls/3892, but that has not
been released because 4.0.0 has not yet been released.

Another relevant issue: aio-libs/aiohttp#4600.

ci/ci/ci.py

@@ -323,7 +323,11 @@ async def on_startup(app):
         raise_for_status=True,
         timeout=aiohttp.ClientTimeout(total=60))
     app['client_session'] = session
-    app['github_client'] = gh_aiohttp.GitHubAPI(session, 'ci', oauth_token=oauth_token)
+    app['github_client'] = gh_aiohttp.GitHubAPI(
+        aiohttp.ClientSession(
+            timeout=aiohttp.ClientTimeout(total=60)),
+        'ci',
+        oauth_token=oauth_token)
     app['batch_client'] = await BatchClient('ci', session=session)
 
     with open('/ci-user-secret/sql-config.json', 'r') as f:

ci/ci/github.py

@@ -309,7 +309,7 @@ async def post_github_status(self, gh_client, gh_status):
         except gidgethub.HTTPException as e:
             log.info(f'{self.short_str()}: notify github of build state failed due to exception: {e}')
         except aiohttp.client_exceptions.ClientResponseError as e:
-            log.error(f'{self.short_str()}: Unexpected exception in post to github: {e}')
+            log.exception(f'{self.short_str()}: Unexpected exception in post to github: {data} {e}')
 
     async def _update_github(self, gh):
         await self._update_last_known_github_status(gh)