Importing Python random lead to an error

[maximdanilchenko]

Hi!

🌍 Environment

• Your operating system and version:

macOS Mojave 10.14.6

• Your python version:

Tested on 3.8.1 and 3.6.10

• How did you install python (e.g. apt or pyenv)? Did you use a virtualenv?:

I use pyenv

• Your rust version (rustc --version):

rustc 1.43.0-nightly (58b834344 2020-02-05)

• Are you using the latest pyo3 version? Have you tried using latest master?

0.8.4 and master both have this issue

💥 Reproducing

fn main(){
    let gil = Python::acquire_gil();
    let py = gil.python();
    match py.import("random") {
            Err(e) => e.print(py),
            Ok(x) => {},
        }
}

Traceback (most recent call last):
  File "/Users/maksim.danilchenko/.pyenv/versions/3.6.10/lib/python3.6/random.py", line 42, in <module>
    from math import log as _log, exp as _exp, pi as _pi, e as _e, ceil as _ceil
ImportError: dlopen(/Users/maksim.danilchenko/.pyenv/versions/3.6.10/lib/python3.6/lib-dynload/math.cpython-36m-darwin.so, 2): Symbol not found: __PyLong_GCD
  Referenced from: /Users/maksim.danilchenko/.pyenv/versions/3.6.10/lib/python3.6/lib-dynload/math.cpython-36m-darwin.so
  Expected in: flat namespace
 in /Users/maksim.danilchenko/.pyenv/versions/3.6.10/lib/python3.6/lib-dynload/math.cpython-36m-darwin.so

[maximdanilchenko]

#742 (comment) - fixes it, but anyway it is not common way to Install pyenv:)

[kngwyu]

Thank you!
I'll add a note for this on README and the guide.

[movermeyer]

It may be obvious, but this isn't limited to random. You can also reproduce it with datetime, and math.

Traceback (most recent call last):
  File "/Users/my_user/.pyenv/versions/3.8.0/lib/python3.8/datetime.py", line 8, in <module>
    import math as _math
ImportError: dlopen(/Users/my_user/.pyenv/versions/3.8.0/lib/python3.8/lib-dynload/math.cpython-38-darwin.so, 2): Symbol not found: __PyLong_GCD
  Referenced from: /Users/my_user/.pyenv/versions/3.8.0/lib/python3.8/lib-dynload/math.cpython-38-darwin.so
  Expected in: flat namespace

[kngwyu]

I'm still not sure how to deal with pyenv problem.
@movermeyer
If you have any idea, please comment to #763

[davidhewitt]

I am wondering whether it's possible to detect a misconfigured pyenv in build.rs.

I have MBP I can use to test sometime. No promises on exactly when.

[emmatyping]

The sysconfig module CONFIG_ARGS variable has the command line, so it seems simple to check if that contains "--enable-shared"