Handle cache incompatibilities

[jkwill87]

Background

• mapi makes use of requests-cache to cache API provider responses to reduce the number of API calls and increase performance
• request-cache essentially just serializes request binary objects and stores them in a sqlite database
• the format of these objects vary between versions of python so an effort is made to separate py2 and py3 databases so that they can coexist
• unfortunately there are even incompatibilities between different versions of python packages which can surface when a user updates mapi's dependencies :(

Acceptance Criteria

• Invalidate or delete cache on error
• Retry request

Notes

• See Fails with Python 3.4 requests-cache/requests-cache#83