warn instead of raising... for now

edit warning per suggestion

2 files changed, 20 insertions, 15 deletions

diff --git a/dateutil/parser/_parser.py b/dateutil/parser/_parser.py
index a5ec2fb..de81fdc 100644
--- a/dateutil/parser/_parser.py
+++ b/dateutil/parser/_parser.py
@@ -34,6 +34,7 @@ import datetime
 import re
 import string
 import time
+import warnings
 
 from calendar import monthrange
 from io import StringIO
@@ -613,14 +614,6 @@ class parser(object):
         if not ignoretz:
             ret = self._build_tzaware(ret, res, tzinfos)
 
-            elif not res.tzname and not res.tzoffset:
-                # i.e. no timezone information was found.
-                pass
-            else:
-                # tz-like string was parsed but we don't know what to do
-                # with it
-                raise ValueError(res.tzname)
-
         if kwargs.get('fuzzy_with_tokens', False):
             return ret, skipped_tokens
         else:
@@ -1153,9 +1146,18 @@ class parser(object):
         elif res.tzoffset:
             aware = naive.replace(tzinfo=tz.tzoffset(res.tzname, res.tzoffset))
 
-        else:
-            # TODO: this is really only the right thing to do if no tz
-            # information was found.
+        elif not res.tzname and not res.tzoffset:
+            # i.e. no timezone information was found.
+            aware = naive
+
+        elif res.tzname:
+            # tz-like string was parsed but we don't know what to do
+            # with it
+            warnings.warn("tzname {tzname} identified but not understood.  "
+                          "Pass `tzinfos` argument in order to correctly "
+                          "return a timezone-aware datetime.  In a future "
+                          "version, this raise an "
+                          "exception.".format(tzname=res.tzname))
             aware = naive
 
         return aware
diff --git a/dateutil/test/test_parser.py b/dateutil/test/test_parser.py
index ce27e82..961ae3d 100644
--- a/dateutil/test/test_parser.py
+++ b/dateutil/test/test_parser.py
@@ -574,8 +574,9 @@ class ParserTest(unittest.TestCase):
 
     def testFuzzyIgnoreAMPM(self):
         s1 = "Jan 29, 1945 14:45 AM I going to see you there?"
-
-        self.assertEqual(parse(s1, fuzzy=True), datetime(1945, 1, 29, 14, 45))
+        with pytest.warns(UserWarning, match="identified but not understood"):
+            res = parse(s1, fuzzy=True)
+        self.assertEqual(res, datetime(1945, 1, 29, 14, 45))
 
     def testExtraSpace(self):
         self.assertEqual(parse("  July   4 ,  1976   12:01:02   am  "),
@@ -683,8 +684,10 @@ class ParserTest(unittest.TestCase):
                          datetime(2003, 9, 25, 12, 8))
 
     def testRandomFormat26(self):
-        self.assertEqual(parse("5:50 A.M. on June 13, 1990"),
-                         datetime(1990, 6, 13, 5, 50))
+        with pytest.warns(UserWarning, match="identified but not understood"):
+            res = parse("5:50 A.M. on June 13, 1990")
+
+        self.assertEqual(res, datetime(1990, 6, 13, 5, 50))
 
     def testRandomFormat27(self):
         self.assertEqual(parse("3rd of May 2001"), datetime(2001, 5, 3))