fix(exception-handling): Catch errors when requesting datafile

[aliabbasrizvi]

Summary

We were not catching all exceptions when requesting the datafile. The HTTPError class is only a single class of errors and we were not capturing all the other errors like timeout issues, proxy issues, etc.

The class of exceptions can be seen here: https://requests.readthedocs.io/en/master/_modules/requests/exceptions

Updating to catch RequestException. It is also something we were already doing correctly in event dispatching: https://github.com/optimizely/python-sdk/blob/master/optimizely/event_dispatcher.py#L42

Test plan

• Tested timeout before and after the fix.
• Unit test added.

[mikeproeng37]

Nice catch. Can we add some unit tests to make sure that we handle exceptions other than HTTPError?

[coveralls]

Coverage remained the same at 97.096% when pulling b2ef8f1 on ali/fix_error_handling into 3e0fa0a on master.

[mikeproeng37]

lgtm

[aliabbasrizvi]

Tests had passed: https://travis-ci.org/github/optimizely/python-sdk/builds/706967427. Going to force merge.

[mikeproeng37]

Go for it! Travis has been misbehaving lately...