`pdbpp` borks our `0.1.0a5` on `pypi` 😂

[goodboy]

Not sure why I'm surprised; every time I try to release something moderately "bleeding edge" pypi stuff never works.

This one may have been a newb mistake though:

ERROR: Packages installed from PyPI cannot depend on packages which are not also hosted on PyPI.
tractor depends on pdbpp@ git+https://github.com/pdbpp/pdbpp@76c4be5#egg=pdbpp ; python_version > "3.9"

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Related discussion around why this is the case can be found here: https://discuss.python.org/t/packages-installed-from-pypi-cannot-depend-on-packages-which-are-not-also-hosted-on-pypi/3736.

I'm not super interested in vendoring pdbpp so a better stop gap if that project is taking too long is to maybe offer debug mode as an extra dep?

Users can just install from git for now since I don't really have the time to get all the pdbpp deps in line for 3.10.

Relates to following pdbpp outstandings:

• https://github.com/pdbpp/pdbpp/issues/498
• maybe https://github.com/pdbpp/pdbpp/issues/496
• https://github.com/pdbpp/pdbpp/issues/480