Issue2495: tokenize.untokenize did not insert space between two consecutive string literals:
"" "" => """", which is invalid code.

Will backport
diff --git a/Lib/test/test_tokenize.py b/Lib/test/test_tokenize.py
index c29728f..ae5f410 100644
--- a/Lib/test/test_tokenize.py
+++ b/Lib/test/test_tokenize.py
@@ -487,13 +487,18 @@
     >>> roundtrip("# Comment \\\\nx = 0")
     True
 
+Two string literals on the same line
+
+    >>> roundtrip("'' ''")
+    True
+
+Test roundtrip on random python modules.
+pass the '-ucompiler' option to process the full directory.
+
     >>>
     >>> tempdir = os.path.dirname(f) or os.curdir
     >>> testfiles = glob.glob(os.path.join(tempdir, "test*.py"))
 
-    XXX: tokenize doesn not support __future__.unicode_literals yet
-    >>> blacklist = ("test_future4.py",)
-    >>> testfiles = [f for f in testfiles if not f.endswith(blacklist)]
     >>> if not test_support.is_resource_enabled("compiler"):
     ...     testfiles = random.sample(testfiles, 10)
     ...