scrapyd-deploy with "deploy failed (400)"

Question

I am trying to deploy with scrapyd-deploy to a remote scrapyd server, which failes without error message:

% scrapyd-deploy                                                       
/Library/Frameworks/Python.framework/Versions/3.8/bin/scrapyd-deploy:23: ScrapyDeprecationWarning: Module `scrapy.utils.http` is deprecated, Please import from `w3lib.http` instead.
  from scrapy.utils.http import basic_auth_header
fatal: No names found, cannot describe anything.
Packing version r3-master
Deploying to project "crawler" in http://ip:6843/addversion.json
Deploy failed (400):

No further error message has been displayed. Can somebody help to resolve this?

Answer 1

Moved from comment to answer:
In a similar sounding issue with the same error-code the problem was that Twisted versions earlier than 18.9 don't support python-3.7. If you are using python-3.7 and your twisted version is below 18.9, try upgrading twisted to at least version 18.9:

pip install -U Twisted==18.9.0