yum TumRepository.dump() function cannot be used as a .repo file Add a
new function to write this in the correct format, and limited to the
fields we use.
Add a test for the new function.
Fix /projects/source/info to return an error 400 if a nonexistant TOML
source is requested. If JSON is used the error is part of the standard
response.
Update test_server.py to check for the correct error code.
When running tests somewhere else than Central Time, `test_api_time()`
fails like
AssertionError: '1985-10-27T02:00:00' != '1985-10-26T21:00:00'
`test_yaps_to_project_info()` fails in a similar way.
Pin the time zone to UTC for this test and adjust timestamps to UTC.
