Make substitution engine ignore factor arrays, fix #302

The fix assumes, that the bug was that the substitution engine -
tox.config.Replacer, while recursvely replacing references to actual
values, treated factor arrays (like {py27,py34}) as references, that
are needed to be replaced, which they are not.

The patch simply amends regex which is used by Replacer to recognize
references, to ignore factor arrays. And factor arrays assumed to be
values, enclosed in curly braces, that contain at least one comma.

--HG--
branch : issue302

tests/test_config.py

@@ -1154,20 +1154,32 @@ def test_rewrite_simple_posargs(self, tmpdir, newconfig):
         argv = conf.commands
         assert argv[0] == ["cmd1", "hello"]
 
-    def test_take_dependencies_from_other_testenv(self, newconfig):
+    @pytest.mark.parametrize('envlist, deps', [
+        (['py27'], ('pytest', 'pytest-cov')),
+        (['py27', 'py34'], ('pytest', 'py{27,34}: pytest-cov')),
+    ])
+    def test_take_dependencies_from_other_testenv(
+        self,
+        newconfig,
+        envlist,
+        deps
+    ):
         inisource = """
+            [tox]
+            envlist = {envlist}
             [testenv]
-            deps=
-                pytest
-                pytest-cov
+            deps={deps}
             [testenv:py27]
             deps=
-                {[testenv]deps}
+                {{[testenv]deps}}
                 fun
-        """
+        """.format(
+            envlist=','.join(envlist),
+            deps='\n' + '\n'.join([' ' * 17 + d for d in deps])
+        )
         conf = newconfig([], inisource).envconfigs['py27']
         packages = [dep.name for dep in conf.deps]
-        assert packages == ['pytest', 'pytest-cov', 'fun']
+        assert packages == list(deps) + ['fun']
 
     def test_take_dependencies_from_other_section(self, newconfig):
         inisource = """

tox/config.py

@@ -1017,7 +1017,7 @@ class Replacer:
         r'''
         (?<!\\)[{]
         (?:(?P<sub_type>[^[:{}]+):)?    # optional sub_type for special rules
-        (?P<substitution_value>[^{}]*)  # substitution key
+        (?P<substitution_value>[^,{}]*)  # substitution key
         [}]
         ''', re.VERBOSE)