Raise error when GitLab module fails to connect

[jhutar]

What about this?

diff --git a/did/plugins/gitlab.py b/did/plugins/gitlab.py
index b546e44..52f75d8 100644
--- a/did/plugins/gitlab.py
+++ b/did/plugins/gitlab.py
@@ -69,6 +69,7 @@ class GitLab(object):
             self, endpoint, since=None, get_all_results=False):
         results = []
         result = self._get_gitlab_api(endpoint)
+        result.raise_for_status()
         results.extend(result.json())
         while ('next' in result.links and 'url' in result.links['next'] and
                 get_all_results):

or maybe just a warning like:

if not result.ok:
    logging.warning("Error {0}: {1}".format(result.status_code, result.text))

In my case, looks like I'm using some buggy GitLab version and API token with "read_user" was not enough. I have been experimenting for some time and discovered GitLab was correctly giving me the reason, but it was hidden:

requests.exceptions.HTTPError: 403 Client Error: Forbidden for url: https://.../api/v4/users/1333/events?after=2018-10-01&before=2018-11-02

[psss]

Makes sense, thanks for the patch.