Do we need to do something about these tox warnings?

```
=============================== warnings summary ===============================

ceph_salt/config_shell.py:1199

/home/travis/build/ceph/ceph-salt/ceph_salt/config_shell.py:1199: DeprecationWarning: invalid escape sequence \+

var = QuotedString('"') | QuotedString("'") | Word(alphanums + '?;&*$!#,=_\+/.<>()~@:-%[]')

ceph_salt/config_shell.py:1201

/home/travis/build/ceph/ceph-salt/ceph_salt/config_shell.py:1201: DeprecationWarning: invalid escape sequence \-

keyword = Word(alphanums + '_\-')

ceph_salt/config_shell.py:1207

ceph_salt/config_shell.py:1207

/home/travis/build/ceph/ceph-salt/ceph_salt/config_shell.py:1207: DeprecationWarning: invalid escape sequence \[

pathstd = Regex('([A-Za-z0-9:_.\[\]]|-)*' + '/' + '([A-Za-z0-9:_.\[\]/]|-)*') | '..' | '.'

.tox/py36/lib/python3.6/distutils/__init__.py:4

/home/travis/build/ceph/ceph-salt/.tox/py36/lib/python3.6/distutils/__init__.py:4: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses

import imp
```

Inspect the warnings at ceph_salt/config_shell.py lines 1199, 1201, and 1207, then rerun the tox environment to confirm which warnings remain. Also check the reported .tox/py36/distutils warning; done means the relevant tox run no longer emits the actionable warnings.

Written by the indexing model from the issue text.