#1155362: allow hh:mm:ss-uuuu like we allow hh:mm:ss+uuuu in parsedate_tz

Original patch by Thomas Herve.
diff --git a/Lib/email/_parseaddr.py b/Lib/email/_parseaddr.py
index 699d418..41694f9 100644
--- a/Lib/email/_parseaddr.py
+++ b/Lib/email/_parseaddr.py
@@ -64,8 +64,10 @@
     if len(data) == 4:
         s = data[3]
         i = s.find('+')
+        if i == -1:
+            i = s.find('-')
         if i > 0:
-            data[3:] = [s[:i], s[i+1:]]
+            data[3:] = [s[:i], s[i:]]
         else:
             data.append('') # Dummy tz
     if len(data) < 5: