work around Python's graceless handling of invalid LANG

NEWS

@@ -7,6 +7,9 @@
   applied was always just alphabetical by filename, which is frequently
   but not always what you want.
 * Fix crash in lastid when the artist name is not available.
+* Fixed a spurious crash when LANG or a related environment variable is
+  set to an invalid value (such as 'UTF-8' on some installations of Mac
+  OS X).
 
 1.0b5
 -----

beets/ui/__init__.py

@@ -59,7 +59,12 @@ def print_(*strings):
     else:
         txt = u''
     if isinstance(txt, unicode):
-        encoding = locale.getdefaultlocale()[1] or 'utf8'
+        try:
+            encoding = locale.getdefaultlocale()[1] or 'utf8'
+        except ValueError:
+            # Invalid locale environment variable setting. To avoid
+            # failing entirely for no good reason, assume UTF-8.
+            encoding = 'utf8'
         txt = txt.encode(encoding, 'replace')
     print txt
 

test/test_ui.py

@@ -78,9 +78,29 @@ class PrintTest(unittest.TestCase):
             ui.print_(u'something')
         except TypeError:
             self.fail('TypeError during print')
+        finally:
+            if lang:
+                os.environ['LANG'] = lang
 
-        if lang:
-            os.environ['LANG'] = lang
+    def test_print_with_invalid_locale(self):
+        old_lang = os.environ.get('LANG')
+        os.environ['LANG'] = ''
+        old_ctype = os.environ.get('LC_CTYPE')
+        os.environ['LC_CTYPE'] = 'UTF-8'
+
+        try:
+            ui.print_(u'something')
+        except ValueError:
+            self.fail('ValueError during print')
+        finally:
+            if old_lang:
+                os.environ['LANG'] = old_lang
+            else:
+                del os.environ['LANG']
+            if old_ctype:
+                os.environ['LC_CTYPE'] = old_ctype
+            else:
+                del os.environ['LC_CTYPE']
 
 def suite():
     return unittest.TestLoader().loadTestsFromName(__name__)