Some tests use the `client` fixture but don’t call any of its methods.
The reason for doing this is because the test depends on something in
the request context.
This commit replaces all those instances with `client_request`, which
also sets the request context.
These tests are the last ones that still use the `client` fixture. By
replacing it with `client_request` we will be able to say that no tests
should be using the `client` fixture directly.
We don’t want to muddy them up with the normal CSV uploads.
I’ve tried to reuse the existing S3 code where possible because it’s
well tested.
Buckets have already been created.
Separated s3_client.py into 3 files - for logos, CSV files and the MOU.
This helps to keep things clearer now that we need to add lots more logo
functions for letters.
