Regexp validate fails if meta-character like '\w' is used in Python 2.7

[lmazuel]

Example in Python 2.7:

>>> re.match('^[-\\w\\._\\(\\)]+$', u'éééé') # No match
>>> re.match('^[-\\w\\._\\(\\)]+$', u'éééé', re.U)
<_sre.SRE_Match object at 0x03935F70>

In Python 3.x both works

Need to add the re.UNICODE flag to all re calls in msrest

[lmazuel]

In real package, prevents a user to create/get/delete a RG in Py2.7 (regexp is '^[-\\w\\._\\(\\)]+$'). FYI @derekbekoe @johanste

Also FYI @annatisch @brettcannon