Base class for all errors

Closes #43

2 files changed, 14 insertions, 2 deletions

diff --git a/src/pytz/exceptions.py b/src/pytz/exceptions.py
index 18df33e..4b20bde 100644
--- a/src/pytz/exceptions.py
+++ b/src/pytz/exceptions.py
@@ -8,7 +8,11 @@ __all__ = [
 ]
 
 
-class UnknownTimeZoneError(KeyError):
+class Error(Exception):
+    '''Base class for all exceptions raised by the pytz library'''
+
+
+class UnknownTimeZoneError(KeyError, Error):
     '''Exception raised when pytz is passed an unknown timezone.
 
     >>> isinstance(UnknownTimeZoneError(), LookupError)
@@ -20,11 +24,18 @@ class UnknownTimeZoneError(KeyError):
 
     >>> isinstance(UnknownTimeZoneError(), KeyError)
     True
+
+    And also a subclass of pytz.exceptions.Error, as are other pytz
+    exceptions.
+
+    >>> isinstance(UnknownTimeZoneError(), Error)
+    True
+
     '''
     pass
 
 
-class InvalidTimeError(Exception):
+class InvalidTimeError(Error):
     '''Base class for invalid time exceptions.'''
 
 
diff --git a/src/pytz/tests/test_tzinfo.py b/src/pytz/tests/test_tzinfo.py
index 7d759af..35430e8 100644
--- a/src/pytz/tests/test_tzinfo.py
+++ b/src/pytz/tests/test_tzinfo.py
@@ -859,6 +859,7 @@ def test_suite():
     suite = unittest.TestSuite()
     suite.addTest(doctest.DocTestSuite('pytz'))
     suite.addTest(doctest.DocTestSuite('pytz.tzinfo'))
+    suite.addTest(doctest.DocTestSuite('pytz.exceptions'))
     import test_tzinfo
     suite.addTest(unittest.defaultTestLoader.loadTestsFromModule(test_tzinfo))
     return suite