More gdb test guards.

runtests.py

@@ -645,7 +645,11 @@ class CythonUnitTestCase(CythonCompileTestCase):
             pass
 
 
-include_debugger = sys.version_info[:2] > (2, 5)
+try:
+    import gdb
+    include_debugger = sys.version_info[:2] > (2, 5)
+except:
+    include_debugger = False
 
 def collect_unittests(path, module_prefix, suite, selectors):
     def file_matches(filename):
@@ -703,8 +707,9 @@ def collect_doctests(path, module_prefix, suite, selectors):
                 filename in blacklist)
     import doctest, types
     for dirpath, dirnames, filenames in os.walk(path):
-        parentname = os.path.split(dirpath)[-1]
-        if package_matches(parentname):
+        for dir in list(dirnames):
+            if not package_matches(dir):
+                dirnames.remove(dir)
         for f in filenames:
             if file_matches(f):
                 if not f.endswith('.py'): continue