Invalid escape sequence fixes (#638)

* Python 3.6 invalid escape sequence deprecation fixes

https://docs.python.org/3/whatsnew/3.6.html#deprecated-python-behavior

* Make version from basename getter regex simpler and stricter

Was missing a backslash from tar matcher.

tests/test_config.py

@@ -1201,7 +1201,7 @@ def test_substitution_double(self, newconfig):
         assert argv[0] == ['echo', 'bah']
 
     def test_posargs_backslashed_or_quoted(self, tmpdir, newconfig):
-        inisource = """
+        inisource = r"""
             [testenv:py27]
             commands =
                 echo "\{posargs\}" = {posargs}

tests/test_interpreters.py

@@ -53,7 +53,7 @@ class envconfig:
         name = "python%s" % ver
         if sys.platform == "win32":
             pydir = "python%s" % ver.replace(".", "")
-            x = py.path.local("c:\%s" % pydir)
+            x = py.path.local(r"c:\%s" % pydir)
             print(x)
             if not x.check():
                 continue

tox/config.py

@@ -927,7 +927,7 @@ def __init__(self, name, url=None):
 
 #: Check value matches substitution form
 #: of referencing value from other section. E.g. {[base]commands}
-is_section_substitution = re.compile("{\[[^{}\s]+\]\S+?}").match
+is_section_substitution = re.compile(r"{\[[^{}\s]+\]\S+?}").match
 
 
 class SectionReader:

tox/interpreters.py

@@ -160,7 +160,7 @@ def tox_get_python_executable(envconfig):
     # Exceptions to the usual windows mapping
     win32map = {
         'python': sys.executable,
-        'jython': "c:\jython2.5.1\jython.bat",
+        'jython': r"c:\jython2.5.1\jython.bat",
     }
 
     def locate_via_py(v_maj, v_min):

tox/session.py

@@ -716,7 +716,7 @@ def _resolvepkg(self, pkgspec):
             return candidates[0]
 
 
-_rex_getversion = re.compile("[\w_\-\+\.]+-(.*)(\.zip|\.tar.gz)")
+_rex_getversion = re.compile(r"[\w_\-\+\.]+-(.*)\.(zip|tar\.gz)")
 
 
 def getversion(basename):