v0.10.1 broke Ubuntu 16.04 install via pip

[mDuo13]

I manage a package (Dactyl) that uses watchdog as a dependency. Starting with the release of Watchdog v0.10.1, our Dockerized builds (Ubuntu 16.04) are failing on an ImportError for pathtools that ultimately comes from watchdog.

After some investigation, it appears to be that pip3 install watchdog no longer installs the necessary pathtools dependency because pip doesn't look at the setup.cfg file. This issue may be masked on some OSes because it's common for pathtools to be installed by default, but I was able to reproduce as follows:

1. Creating a fresh Ubuntu 16.04 install (I did it on a VM)

2. sudo apt-get install python3-pip

3. pip3 install watchdog

4. python3

5. At the Python prompt:

    from watchdog.observers import Observer
   

   The result is similar to this error:

      File "/home/username/.local/lib/python3.5/site-packages/watchdog/observers/__init__.py", line 63, in <module>
        from .inotify import InotifyObserver as Observer
      File "/home/username/.local/lib/python3.5/site-packages/watchdog/observers/inotify.py", line 83, in <module>
        from watchdog.events import (
      File "/home/username/.local/lib/python3.5/site-packages/watchdog/events.py", line 91, in <module>
        from pathtools.patterns import match_any_paths
    ImportError: No module named 'pathtools'
   

Manually installing pathtools with pip fixes the error.

I suspect the changes in commit 6baa210 to remove pathtools from install_requires are the cause.

[BoboTiG]

Hello,

Could you tell us the setuptools version please?

[mDuo13]

Seems to happen with the system-default setuptools version on Ubuntu 16.04, which, I think, is 20.x?

[BoboTiG]

Could you post the output of python -c "import setuptools; print(setuptools.__version__)" (or using python3, the Python you are using for your tests)?
I would like to check if we need to pin a minimum setuptools version before installing watchdog.

[mDuo13]

Using Python 3, yes.

I'll have to get back to you on the exact setuptools version; I don't have the VM up and running at the moment. But, again, this is whatever the default one that comes on Ubuntu 16.04.

Since Watchdog does run great when you install the dependency and Ubuntu 16.04 is going to be supported (therefore common in cloud providers) for another 14 months or so, I would urge you to change the way you specify the dependency (back to how it was) to make it "just work" rather than pinning a minimum version.

[BoboTiG]

The thing is that if we move back to how it was done before the commit, it will break elsewhere (again, because of outdated setuptools).
I will need to do more tests in order to find a good fix for everyone.

[BoboTiG]

I found the right minimum version: 36.2.7.

But I do not know yet how to deal with that :)