Fix build with python 2.4

problem spotted and ok steven@

biology/py-biopython/patches/patch-setup_py

@@ -1,6 +1,6 @@
-$OpenBSD: patch-setup_py,v 1.3 2005/12/03 22:34:52 alek Exp $
---- setup.py.orig	Tue Nov 22 00:13:39 2005
-+++ setup.py	Tue Nov 22 00:13:46 2005
+$OpenBSD: patch-setup_py,v 1.4 2005/12/18 20:33:17 alek Exp $
+--- setup.py.orig	Fri Oct 28 21:41:02 2005
++++ setup.py	Sun Dec 18 19:26:31 2005
 @@ -65,6 +65,7 @@ def check_dependencies_once():
      return _CHECKED
  
@@ -9,3 +9,15 @@ $OpenBSD: patch-setup_py,v 1.3 2005/12/03 22:34:52 alek Exp $
      """Return whether the installation should continue."""
      # There should be some way for the user to tell specify not to
      # check dependencies.  For example, it probably should not if
+@@ -254,7 +255,10 @@ def is_Martel_installed():
+         bundled_martel_version = m.__version__
+     else:
+         bundled_martel_version = None
+-    del sys.modules["Martel"]   # Delete the old version of Martel.
++    try:
++        del sys.modules["Martel"]   # Delete the old version of Martel.
++    except:
++        pass
+ 
+     # Now try and import a Martel that's not bundled with Biopython.
+     # To do that, I need to delete all the references to the current