Fix #693: Python 2.4 incompatibilities

BaseException didn't exist until Python 2.5.  Let's create a helper in
pyversion to check whether we're derived from BaseException on Python
2.5 or better, and just Exception on Python 2.4.

3 files changed, 14 insertions, 3 deletions

diff --git a/nose/failure.py b/nose/failure.py
index d24401c..c5fabfd 100644
--- a/nose/failure.py
+++ b/nose/failure.py
@@ -1,6 +1,7 @@
 import logging
 import unittest
 from traceback import format_tb
+from nose.pyversion import is_base_exception
 
 log = logging.getLogger(__name__)
 
@@ -34,7 +35,7 @@ class Failure(unittest.TestCase):
     
     def runTest(self):
         if self.tb is not None:
-            if isinstance(self.exc_val, BaseException):
+            if is_base_exception(self.exc_val):
                 raise self.exc_val, None, self.tb
             raise self.exc_class, self.exc_val, self.tb
         else:
diff --git a/nose/plugins/capture.py b/nose/plugins/capture.py
index 224f0a5..d9041d8 100644
--- a/nose/plugins/capture.py
+++ b/nose/plugins/capture.py
@@ -13,6 +13,7 @@ import logging
 import os
 import sys
 from nose.plugins.base import Plugin
+from nose.pyversion import is_base_exception
 from nose.util import ln
 from StringIO import StringIO
 
@@ -86,7 +87,7 @@ class Capture(Plugin):
         return self.formatError(test, err)
 
     def addCaptureToErr(self, ev, output):
-        if isinstance(ev, BaseException):
+        if is_base_exception(ev):
             if hasattr(ev, '__unicode__'):
                 # 2.6+
                 try:
diff --git a/nose/pyversion.py b/nose/pyversion.py
index a6ec3f7..14a133e 100644
--- a/nose/pyversion.py
+++ b/nose/pyversion.py
@@ -9,7 +9,7 @@ import nose.util
 
 __all__ = ['make_instancemethod', 'cmp_to_key', 'sort_list', 'ClassType',
            'TypeType', 'UNICODE_STRINGS', 'unbound_method', 'ismethod',
-           'bytes_']
+           'bytes_', 'is_base_exception']
 
 # In Python 3.x, all strings are unicode (the call to 'unicode()' in the 2.x
 # source will be replaced with 'str()' when running 2to3, so this test will
@@ -147,3 +147,12 @@ else:
             return func.func_code.co_flags & CO_GENERATOR != 0
         except AttributeError:
             return False
+
+# Make a function to help check if an exception is derived from BaseException.
+# In Python 2.4, we just use Exception instead.
+if sys.version_info[:2] < (2, 5):
+    def is_base_exception(exc):
+        return isinstance(exc, Exception)
+else:
+    def is_base_exception(exc):
+        return isinstance(exc, BaseException)