Error in MultipartStream should lead to useful error
Summary
See linkahead-pylib#115 for an example, where a bug in a client went undetected for a long time because the server error was not explicit enough.
Expected Behavior
Server should clearly tell that the data stream had formatting problems.
Actual Behavior
It's just an unexpected server error.
Steps to Reproduce the Problem
Specifications
- Version: Current main branch
- Platform: Which operating system, which other relevant software versions?
Possible fixes
Do you have ideas how the issue can be resolved?