New tests:

test_failing_import_sticks -- if an import raises an exception,
        ensure that trying to import it again continues raising exceptions
    test_failing_reload -- if a module loads OK, but a reload raises an
        exception, ensure that the module is still in sys.modules, and
        that its __dict__ reflects as much of the reload attempt as
        succeeded.  That doesn't seem like sane semantics, but it is
        backward-compatible semantics <wink>.

Lib/test/test_import.py

@@ -17,6 +17,15 @@ else:
 # Another brief digression to test the accuracy of manifest float constants.
 import double_const  # don't blink -- that *was* the test
 
+def remove_files(name):
+    for f in (name + os.extsep + "py",
+              name + os.extsep + "pyc",
+              name + os.extsep + "pyo",
+              name + os.extsep + "pyw",
+              name + "$py.class"):
+        if os.path.exists(f):
+            os.remove(f)
+
 def test_with_extension(ext): # ext normally ".py"; perhaps ".pyw"
     source = TESTFN + ext
     pyo = TESTFN + os.extsep + "pyo"
@@ -108,3 +117,78 @@ def test_module_with_large_stack(module):
             os.unlink(fname)
 
 test_module_with_large_stack('longlist')
+
+def test_failing_import_sticks():
+    source = TESTFN + os.extsep + "py"
+    f = open(source, "w")
+    print >> f, "a = 1/0"
+    f.close()
+
+    # New in 2.4, we shouldn't be able to import that no matter how often
+    # we try.
+    sys.path.insert(0, os.curdir)
+    try:
+        for i in 1, 2, 3:
+            try:
+                mod = __import__(TESTFN)
+            except ZeroDivisionError:
+                if TESTFN in sys.modules:
+                    raise TestFailed("damaged module in sys.modules", i)
+            else:
+                raise TestFailed("was able to import a damaged module", i)
+    finally:
+        sys.path.pop(0)
+        remove_files(TESTFN)
+
+test_failing_import_sticks()
+
+def test_failing_reload():
+    # A failing reload should leave the module object in sys.modules.
+    source = TESTFN + os.extsep + "py"
+    f = open(source, "w")
+    print >> f, "a = 1"
+    print >> f, "b = 2"
+    f.close()
+
+    sys.path.insert(0, os.curdir)
+    try:
+        mod = __import__(TESTFN)
+        if TESTFN not in sys.modules:
+            raise TestFailed("expected module in sys.modules")
+        if mod.a != 1 or mod.b != 2:
+            raise TestFailed("module has wrong attribute values")
+
+        # On WinXP, just replacing the .py file wasn't enough to
+        # convince reload() to reparse it.  Maybe the timestamp didn't
+        # move enough.  We force it to get reparsed by removing the
+        # compiled file too.
+        remove_files(TESTFN)
+
+        # Now damage the module.
+        f = open(source, "w")
+        print >> f, "a = 10"
+        print >> f, "b = 20//0"
+        f.close()
+        try:
+            reload(mod)
+        except ZeroDivisionError:
+            pass
+        else:
+            raise TestFailed("was able to reload a damaged module")
+
+        # But we still expect the module to be in sys.modules.
+        mod = sys.modules.get(TESTFN)
+        if mod is None:
+            raise TestFailed("expected module to still be in sys.modules")
+        # We should have replaced a w/ 10, but the old b value should
+        # stick.
+        if mod.a != 10 or mod.b != 2:
+            raise TestFailed("module has wrong attribute values")
+
+    finally:
+        sys.path.pop(0)
+        remove_files(TESTFN)
+        if TESTFN in sys.modules:
+            del sys.modules[TESTFN]
+
+test_failing_reload()