Cache Github History about rdm

[orwonthe]

Here is an example stack dump from hitting the rate limit error:
Traceback (most recent call last): File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/main.py", line 20, in main exit_code = cli(sys.argv[1:]) File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/main.py", line 42, in cli pull_from_project_manager(args.config) File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/pull.py", line 17, in pull_from_project_manager development_history = pm_backend.pull() File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/project_management/github.py", line 50, in pull return _format_development_history(self.config, issues, pull_requests) File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/project_management/github.py", line 71, in _format_development_history changes = [build_change(config, pr) for pr in pull_requests if _is_change(pr)] File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/project_management/github.py", line 71, in <listcomp> changes = [build_change(config, pr) for pr in pull_requests if _is_change(pr)] File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/project_management/github.py", line 132, in build_change approvals = change_approvals(config, pull_request) File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/project_management/github.py", line 194, in change_approvals github_reviews = [r for r in pull_request.get_reviews()] File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/rdm/project_management/github.py", line 194, in <listcomp> github_reviews = [r for r in pull_request.get_reviews()] File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/github/PaginatedList.py", line 59, in __iter__ newElements = self._grow() File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/github/PaginatedList.py", line 71, in _grow newElements = self._fetchNextPage() File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/github/PaginatedList.py", line 204, in _fetchNextPage "GET", self.__nextUrl, parameters=self.__nextParams, headers=self.__headers File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/github/Requester.py", line 319, in requestJsonAndCheck verb, url, parameters, headers, input, self.__customConnection(url) File "/home/willy/code/venv/pc_reg/lib/python3.6/site-packages/github/Requester.py", line 342, in __check raise self.__createException(status, responseHeaders, output) github.GithubException.RateLimitExceededException: 403 {"message": "API rate limit exceeded for user ID 890550.", "documentation_url": "https://docs.github.com/rest/overview/resources-in-the-rest-api#rate-limiting"}

[johndgiese]

Ugh! We should also catch this error and print something more useful than a huge stack trace!