The reason that `pip-tools` running on Python 3 didn’t detect the
right requirements for `thumbor` on Python 2 is simply that some of
them are conditional on the Python version.
As for the requirements that had been manually added as a workaround:
`backports-abc` and `singledispatch` are now correctly detected, while
`backports.ssl-match-hostname` was vendored into `urllib3` some time
ago and `certifi` is no longer necessary.
Signed-off-by: Anders Kaseorg <anders@zulipchat.com>
Anders Kaseorg