Jan KatinsWorkarounds for TypeError: unsupported operand type(s) for -=: 'Retry' and 'int'
Using pip on a Debian/Ubuntu system can result in this error: TypeError:
unsupported operand type(s) for -=: 'Retry' and 'int'. E.g. see this error
report in Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=870701
The problem seems to be that requests/pip vendors some libraries and
Debian/Ubuntu un-vendors them again. This results in the same code imported
multiple times under different names. Funnily the above exception results from
such a mismatch if a network request has an error/ times out. I tried to
follow the explanaition why this results in the above
error, but gave up. :-)
Anyway: we use python3.6 -m venv ... to create virtualenvs and afterwards
pip to install requirements into the virtualenv. Sometimes the error happened
and I couldn’t finish the installations even after multiple tries. As the
problem was that pip uses an un-vendored version of the requests library, the
easiest way to fix it was to switch pip back to use a vendored requests
library:
# this assumes the virtualenv is created in '.venv'
# This will copy the unbundled versions of the libs from /usr/share/python-wheels
# into .venv/share/python-wheels
(md .venv && cd .venv && $(SYSTEM_PYTHON36) -m venv --copies .)
# install a clean copy of requests...
# will also install chardet/idna/urllib3/certifi and so on into .venv
# this might stil fail with the above error...
.venv/bin/pip install requests wheel
# remove the unbundled versions of the libs
(cd .venv/share/python-wheels/ && rm requests-*.whl chardet-*.whl urllib3-*.whl)
Afterwards pip install --requirement=requirements.txt now succeeded.
If you also need a system pip, follow this instructions: https://stackoverflow.com/a/37531821/1380673)