Fix issue 54755 and add regression tests

[dwoz]

What does this PR do?

Address #54755 and add regression tests.

In general we should try to address this kind of thing without mucking around with already imported modules. Ideally we'd recognize that pip was upgraded and re-start the minion automatically. This will however address the bugs reported against the pip_state and other states using the unless requisite.

What issues does this PR fix or reference?

#54755

Previous Behavior

If no pip module is in the python environment imports of the pip state failed with multiple tracebacks. This is due to us trying to del pip when there is no pip variable defined.

New Behavior

Use a purge_pip method before trying to import pip this method will only try to remove the pip module and/or pip variable if it exists.

Tests written?

Yes

Commits signed with GPG?

Yes

[dwoz]

re-run full all

[dwoz]

re-run full all

[codecov]

Codecov Report

Merging #54826 into 2019.2.1 will increase coverage by 31.74%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##           2019.2.1   #54826       +/-   ##
=============================================
+ Coverage      5.02%   36.77%   +31.74%     
=============================================
  Files          1521     1577       +56     
  Lines        253244   269866    +16622     
  Branches      54002    56108     +2106     
=============================================
+ Hits          12734    99238    +86504     
+ Misses       239072   159279    -79793     
- Partials       1438    11349     +9911

Flag	Coverage Δ
#centos7	?
#py2	36.77% <ø> (+31.86%)	⬆️
#py3	?
#tcp	36.77% <ø> (?)
#ubuntu1604	36.77% <ø> (+31.75%)	⬆️
#zeromq	?

Impacted Files	Coverage Δ
salt/proxy/dummy.py	0% <0%> (-80.87%)	⬇️
salt/proxy/docker.py	0% <0%> (-62.5%)	⬇️
salt/proxy/chronos.py	0% <0%> (-50%)	⬇️
salt/proxy/marathon.py	0% <0%> (-50%)	⬇️
salt/transport/frame.py	30.3% <0%> (-46.97%)	⬇️
salt/proxy/cisconso.py	0% <0%> (-46.43%)	⬇️
salt/proxy/arista_pyeapi.py	0% <0%> (-45.66%)	⬇️
salt/proxy/nxos_api.py	0% <0%> (-44.74%)	⬇️
salt/proxy/rest_sample.py	0% <0%> (-38.38%)	⬇️
salt/proxy/netmiko_px.py	0% <0%> (-34.85%)	⬇️
... and 1432 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 433b6fa...602dfa7. Read the comment docs.

[codecov]

Codecov Report

Merging #54826 into 2019.2.1 will increase coverage by 31.74%.
The diff coverage is n/a.

@@              Coverage Diff              @@
##           2019.2.1   #54826       +/-   ##
=============================================
+ Coverage      5.02%   36.77%   +31.74%     
=============================================
  Files          1521     1577       +56     
  Lines        253244   269866    +16622     
  Branches      54002    56108     +2106     
=============================================
+ Hits          12734    99238    +86504     
+ Misses       239072   159279    -79793     
- Partials       1438    11349     +9911

Flag	Coverage Δ
#centos7	?
#py2	36.77% <ø> (+31.86%)	⬆️
#py3	?
#tcp	36.77% <ø> (?)
#ubuntu1604	36.77% <ø> (+31.75%)	⬆️
#zeromq	?

Impacted Files	Coverage Δ
salt/proxy/dummy.py	0% <0%> (-80.87%)	⬇️
salt/proxy/docker.py	0% <0%> (-62.5%)	⬇️
salt/proxy/chronos.py	0% <0%> (-50%)	⬇️
salt/proxy/marathon.py	0% <0%> (-50%)	⬇️
salt/transport/frame.py	30.3% <0%> (-46.97%)	⬇️
salt/proxy/cisconso.py	0% <0%> (-46.43%)	⬇️
salt/proxy/arista_pyeapi.py	0% <0%> (-45.66%)	⬇️
salt/proxy/nxos_api.py	0% <0%> (-44.74%)	⬇️
salt/proxy/rest_sample.py	0% <0%> (-38.38%)	⬇️
salt/proxy/netmiko_px.py	0% <0%> (-34.85%)	⬇️
... and 1432 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 433b6fa...602dfa7. Read the comment docs.