Suddenly I get a lot of errors while trying to use my previously working (for many months) requirements file. I tried to go to the pypi.org and get the same 404 error.
PyPI administrator here. You probably unintentionally had request instead of requests in your requirements.txt file.
request
requests
requirements.txt
These projects (request, get, post) were removed by their author and no longer exist. You should remove them from your requirements.txt file.
get
post