re.compile inference returns incorrect result #520

Steps to reproduce

1. Execute

import astroid
code = """
import re
_ENCODING_RGX = re.compile(r"f")
_ENCODING_RGX #@
"""
print(astroid.extract_node(code).inferred())

This is causing the Travis CI pylint env to fail with:

************* Module astroid.builder
E: 64,20: Instance of 'str' has no 'match' member (no-member)

Current behavior

The above prints [Uninferable, <Const.str l.3 at 0x79558a71e7f0>]

Expected behavior

Should return an Instance of _sre.SRE_Pattern

python -c "from astroid import __pkginfo__; print(__pkginfo__.version)" output

5d21b20