pip-and-virtualenv removes system python packages on fedora 29 but some tools require them

[Ian Wienand]

on fedora29, pip installs into separate locations. Several tools run with "/usr/bin/python3 -Es" which removes the pip path from the invocation.

pip-and-virtualenv has cleared out the system versions of pip/virtualenv etc in an effort to not have them conflict. But now these system tools can't find important packages, leading to things like

---
[root@fedora-29-inap-mtl01-0002083442 ~]# /usr/bin/python3 -Es
Python 3.7.2 (default, Jan 3 2019, 09:14:01)
[GCC 8.2.1 20181215 (Red Hat 8.2.1-6)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import seobject
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.7/site-packages/seobject.py", line 34, in <module>
    import sepolicy
  File "/usr/lib/python3.7/site-packages/sepolicy/__init__.py", line 9, in <module>
    import setools
  File "/usr/lib64/python3.7/site-packages/setools/__init__.py", line 78, in <module>
    from .permmap import PermissionMap
  File "/usr/lib64/python3.7/site-packages/setools/permmap.py", line 25, in <module>
    import pkg_resources
ModuleNotFoundError: No module named 'pkg_resources'
>>>
---

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/633141

[Ian Wienand (iwienand)]

With the fix, there is another problem now:

---
$ semanage
Traceback (most recent call last):
  File "/usr/sbin/semanage", line 28, in <module>
    import seobject
  File "/usr/lib/python3.7/site-packages/seobject.py", line 34, in <module>
    import sepolicy
  File "/usr/lib/python3.7/site-packages/sepolicy/__init__.py", line 9, in <module>
    import setools
  File "/usr/lib64/python3.7/site-packages/setools/__init__.py", line 24, in <module>
    __version__ = pkg_resources.get_distribution("setools").version
AttributeError: module 'pkg_resources' has no attribute 'get_distribution'
---

this seems to be related to https://bugzilla.redhat.com/show_bug.cgi?id=1550368#c21

---
The problem seems to stem from the fact that python3's pip is set to install only to the `/usr/local/lib/` prefix, but if it encounters an older version in `/usr/lib/` it will happily remove it. The result is that programs that run in isolated environment (that don't see into `/usr/local/lib/`) can't find setuptools and crash.
---

[Ian Wienand (iwienand)]

Testing with this change on a Fedora29 + pip-and-virtualenv the semanage tool seems to work ok now

---
bash-4.4# dnf install policycoreutils-python-utils

bash-4.4# semanage
usage: semanage [-h]
                {import,export,login,user,port,ibpkey,ibendport,interface,module,node,fcontext,boolean,permissive,dontaudit}
                ...
semanage: error: the following arguments are required: subcommand
---

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/633141
Committed: https://git.openstack.org/cgit/openstack/diskimage-builder/commit/?id=ea1735b6a259c5424d2a0ca52eca371bf9213ac9
Submitter: Zuul
Branch: master

commit ea1735b6a259c5424d2a0ca52eca371bf9213ac9
Author: Ian Wienand <email address hidden>
Date: Fri Jan 25 16:27:49 2019 +1100

    pip-and-virtualenv : only remove system files on centos

    As described inline, we only want to remove the system package files
    on centos; it causes problems on Fedora where some system tools expect
    these to be there.

    But there is an additional bug -- pip actually removes the system
    package files anyway. To work around this, reinstall the system
    package.

    Closes-Bug: #1813232
    Change-Id: I041a141366099093805e6052b1bbf64efd277e1e