pvesh: Fix invalid string escape sequences

In Python, only a [limited set of characters][0] can be escaped with a
backslash. In recent versions of Python, attempting to escape a
non-escapeable character [raises a SyntaxWarning][1], polluting the
playbook output with warnings like:

    <unknown>:59: SyntaxWarning: invalid escape sequence '\('
    <unknown>:60: SyntaxWarning: invalid escape sequence '\.'
    <unknown>:61: SyntaxWarning: invalid escape sequence '\.'

This commit adds the string literal prefix 'r' to regular expressions in
pvesh.py to ensure that escape sequences are not interpreted in the
given strings. As there were no valid escape sequences in those strings
to begin with, the actual string content remains the same.

[0]: https://docs.python.org/3/reference/lexical_analysis.html#escape-sequences
[1]: python/cpython#98401

module_utils/pvesh.py

@@ -57,9 +57,9 @@ def run_command(handler, resource, **params):
 
         if handler == "get":
             if any(re.match(pattern, stderr[0]) for pattern in [
-                "^no such user \('.{3,64}?'\)$",
-                "^(group|role|pool) '[A-Za-z0-9\.\-_]+' does not exist$",
-                "^domain '[A-Za-z][A-Za-z0-9\.\-_]+' does not exist$"]):
+                r"^no such user \('.{3,64}?'\)$",
+                r"^(group|role|pool) '[A-Za-z0-9\.\-_]+' does not exist$",
+                r"^domain '[A-Za-z][A-Za-z0-9\.\-_]+' does not exist$"]):
                 return {u"status": 404, u"message": stderr[0]}
 
         # This will occur when a param is invalid