Backblaze
the uploader does not check for maximum number of custom header fields
when one passes a dict to file_info it is not checked whether too many entries fields are present.
Cryptic error is thrown, ie:
FAILED to upload after 5 tries. Encountered exceptions: Broken pipe: unable to send entire request
We will implement an extension to b2sdk soon, that will allow for better and faster error reporting on upload attempts.
Unfortunately we cannot implement yet due to urllib3 and requests not supporting Expect: 100 continue headers. We are considering switching to pycurl, but not as soon we've hoped.
I'd rather do this and let the server perform the verification, than implement the verification on the side of b2sdk - if one day limits are changed, b2sdk would not validate the input correctly. On the other hand, we can trust the server to do it well.