Comment # 2 on bug 1218995 from Martin Sirringhaus

Also seeing this on SLES.

This is a weird one.

> mach/site.py", line 1132, in _ensure_python_exe
> [ 2785s]  0:34.01     raise Exception(
> [ 2785s]  0:34.01 Exception: Neither a "python" or "python3" were found. This  means something unexpected happened during the virtual environment creation and we cannot proceed.

From what I can tell in the code, it simply calls `python3 -m venv
--without-pip /some/tmp/dir` [1], and afterwards checks if a python-binary
exists in the newly created venv [2].

There seems to be some race condition, when creating the venv. Maybe in the
filesystem or in python? I don't know how python creates these, but maybe the
process exits before everything is in place?

Matej, could you maybe give some input?

[1]: https://searchfox.org/mozilla-central/source/python/mach/mach/site.py#1170
[2]: https://searchfox.org/mozilla-central/source/python/mach/mach/site.py#1112