Catch warnings in test_translate_existing.

Otherwise a warning is printed each time you run the tests.

src/zope/tal/talgettext.py

@@ -34,6 +34,7 @@
 import time
 import getopt
 import traceback
+import warnings
 
 from zope.interface import implementer
 from zope.tal.htmltalparser import HTMLTALParser
@@ -137,16 +138,16 @@ def translate(self, msgid, domain=None, mapping=None, default=None,
                                         for location in domain[msgid]])
                 # Note: a lot of encode calls here are needed so
                 # Python 3 does not break.
-                print(("Warning: msgid '%s' in %s already exists "
-                       "with a different default (bad: %s, should be: %s)\n"
-                       "The references for the existent value are:\n%s\n" %
-                       (msgid.encode('utf-8'),
-                        self.file.encode('utf-8') + ':'.encode('utf-8')
-                        + str(position).encode('utf-8'),
-                        msgid.default.encode('utf-8'),
-                        existing_msgid.default.encode('utf-8'),
-                        references.encode('utf-8'))),
-                      file=sys.stderr)
+                warnings.warn(
+                    "Warning: msgid '%s' in %s already exists "
+                    "with a different default (bad: %s, should be: %s)\n"
+                    "The references for the existent value are:\n%s\n" %
+                    (msgid.encode('utf-8'),
+                     self.file.encode('utf-8') + ':'.encode('utf-8')
+                     + str(position).encode('utf-8'),
+                     msgid.default.encode('utf-8'),
+                     existing_msgid.default.encode('utf-8'),
+                     references.encode('utf-8')))
         domain[msgid].append((self.file, position))
         return 'x'
 

src/zope/tal/tests/test_talgettext.py

@@ -15,6 +15,7 @@
 """
 import sys
 import unittest
+import warnings
 
 try:
     # Python 2.x
@@ -76,8 +77,13 @@ def test_translate_existing(self):
                          default=u'Read more\u2026', position=13)
         # Adding the same key with a different default is bad and
         # triggers a warning.
-        engine.translate('foo', 'domain',
-                         default='Read still more…', position=42)
+        with warnings.catch_warnings(record=True) as log:
+            warnings.simplefilter("always")
+            engine.translate('foo', 'domain',
+                             default='Read still more…', position=42)
+            self.assertEqual(len(log), 1)
+            self.assertTrue("already exists with a different default"
+                            in log[0].message.message)
 
     def test_dynamic_msgids(self):
         sample_source = """