Repository: googleapis/google-cloud-python

Issue:
BigQuery: Add BadGateway to DEFAULT_RETRY predicate
OS: Linux dc32b7e8763a 4.9.0-6-amd64 #1 SMP Debian 4.9.82-1+deb9u3 (2018-03-02) x86_64 x86_64 x86_64 GNU/Linux
Python version: Python 2.7.6
google-cloud-bigquery: 1.5.0

I'm getting BadGateway exceptions periodically when running queries with the default retry object. Here's an example (relevant part of the stack trace):

```
  File "/opt/conda/lib/python2.7/site-packages/google/cloud/bigquery/job.py", line 2605, in done
    location=self.location)
  File "/opt/conda/lib/python2.7/site-packages/google/cloud/bigquery/client.py", line 579, in _get_query_results
    retry, method='GET', path=path, query_params=extra_params)
  File "/opt/conda/lib/python2.7/site-packages/google/cloud/bigquery/client.py", line 331, in _call_api
    return call()
  File "/opt/conda/lib/python2.7/site-packages/google/api_core/retry.py", line 260, in retry_wrapped_func
    on_error=on_error,
  File "/opt/conda/lib/python2.7/site-packages/google/api_core/retry.py", line 177, in retry_target
    return target()
  File "/opt/conda/lib/python2.7/site-packages/google/cloud/_http.py", line 293, in api_request
    raise exceptions.from_http_response(response)
BadGateway: 502 GET https://www.googleapis.com/bigquery/v2/projects/packard-campbell-synth/queries/c4af3c68-d204-455e-877f-9f81e1c77d68?maxResults=0: <!DOCTYPE html>
<html lang=en>
  <meta charset=utf-8>
  <meta name=viewport content="initial-scale=1, minimum-scale=1, width=device-width">
  <title>Error 502 (Server Error)!!1</title>
  <style>
    *{margin:0;padding:0}html,code{font:15px/22px arial,sans-serif}html{background:#fff;color:#222;padding:15px}body{margin:7% auto 0;max-width:390px;min-height:180px;padding:30px 0 15px}* > body{background:url(//www.google.com/images/errors/robot.png) 100% 5px no-repeat;padding-right:205px}p{margin:11px 0 22px;overflow:hidden}ins{color:#777;text-decoration:none}a img{border:0}@media screen and (max-width:772px){body{background:none;margin-top:0;max-width:none;padding-right:0}}#logo{background:url(//www.google.com/images/branding/googlelogo/1x/googlelogo_color_150x54dp.png) no-repeat;margin-left:-5px}@media only screen and (min-resolution:192dpi){#logo{background:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) no-repeat 0% 0%/100% 100%;-moz-border-image:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) 0}}@media only screen and (-webkit-min-device-pixel-ratio:2){#logo{background:url(//www.google.com/images/branding/googlelogo/2x/googlelogo_color_150x54dp.png) no-repeat;-webkit-background-size:100% 100%}}#logo{display:inline-block;height:54px;width:150px}
  </style>
  <a href=//www.google.com/><span id=logo aria-label=Google></span></a>
  <p><b>502.</b> <ins>That’s an error.</ins>
  <p>The server encountered a temporary error and could not complete your request.<p>Please try again in 30 seconds.  <ins>That’s all we know.</ins>
```

It would be useful to add this to the DEFAULT_RETRY object in https://github.com/GoogleCloudPlatform/google-cloud-python/blob/master/bigquery/google/cloud/bigquery/retry.py.


Discussion:

Resolving patch:
diff --git a/bigquery/google/cloud/bigquery/retry.py b/bigquery/google/cloud/bigquery/retry.py
--- a/bigquery/google/cloud/bigquery/retry.py
+++ b/bigquery/google/cloud/bigquery/retry.py
@@ -20,6 +20,7 @@
     'backendError',
     'rateLimitExceeded',
     'internalError',
+    'badGateway',
 ])
 
 


Test patch:
diff --git a/bigquery/tests/unit/test_retry.py b/bigquery/tests/unit/test_retry.py
--- a/bigquery/tests/unit/test_retry.py
+++ b/bigquery/tests/unit/test_retry.py
@@ -51,3 +51,8 @@ def test_w_internalError(self):
         exc = mock.Mock(
             errors=[{'reason': 'internalError'}], spec=['errors'])
         self.assertTrue(self._call_fut(exc))
+
+    def test_w_badGateway(self):
+        exc = mock.Mock(
+            errors=[{'reason': 'badGateway'}], spec=['errors'])
+        self.assertTrue(self._call_fut(exc))