Installation fails on pkgconfig AttributeError

[raymondEhlers]

When installing lz4 via pip with python 3.6, I received the following AttributeError related to pkgconfig:

test@e75e445ebc4d:/opt/test$ pip install --user lz4
Collecting lz4
  Downloading https://files.pythonhosted.org/packages/f1/4f/878f1827042c5b6828bc23d160f31e242ec820810b8bd04b30b631029952/lz4-2.1.2.tar.gz (128kB)
    100% |████████████████████████████████| 133kB 2.6MB/s
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-842vmqmd/lz4/setup.py", line 34, in <module>
        liblz4_found = pkgconfig_installed('liblz4', LZ4_REQUIRED_VERSION, default=False)
      File "/tmp/pip-install-842vmqmd/lz4/setup.py", line 24, in pkgconfig_installed
        installed = pkgconfig.installed(lib, required_version)
    AttributeError: module 'pkgconfig' has no attribute 'installed'

    ----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /tmp/pip-install-842vmqmd/lz4/

In trying to reproduce it, I found the issue is caused by some third party software which sets the PYTHONPATH to a directory which includes an empty pkgconfig directory... I realize that this is a bit of a silly issue, and is mostly unrelated to lz4 (I will try to get the third party software to fix it), but I imagine that other software could also cause this same issue.

So I would argue that it's worth addressing. I think it can be addressed with a small modification of the lz4 setup.py by adding around line 25:

 try:
   installed = pkgconfig.installed(lib, required_version
except AttributeError:
  # Problem with pkgconfig package
  pass
...

I'm happy to open a PR if you'd like. Please let me know what you think. Thanks!

[jonathanunderwood]

Thanks for the report. My initial thoughts are:

• Working around horribly broken unrelated software is not really in scope - that problem really needs fixing, it's pretty bad to override PYTHONPATH and break packages like that.
• Simply passing on the exception isn't the right fix, as we're using pkgconfig to determine if there's a suitable system installed lz4 library.

On the otherhand, this is perhaps another valid case for falling back to building against the bundled lz4, so I'm not entirely opposed.

[jonathanunderwood]

A better fix would be to change the import around line 16 to import the pkgconfig.installed function there (rather than just the package), and then use that. So something like:

try:
    import pkgconfig.installed as pkgconfig_installed
except ImportError:
    # pkgconfig is not installed. It will be installed by setup_requires.
    pass
...

I won't get chance to add a commit for this until the weekend, so if you had time to make a PR, that would be cool :)

[raymondEhlers]

Thanks for bearing with me on this out of scope issue - I very much agree that the other software is breaking things in a really bad way (I've reported it, so I hope that they'll fix it). But I also really appreciate you considering a fall back here :-)

You're right that my solution wasn't really the best way to go about fixing it - I'll open a PR that implements your suggestion

[raymondEhlers]

Addressed in #160