[Twisted-Python] which dia error from lore

[Andrea Arcangeli]

mktap is spawning an error (which dia not found), this fixed it

Index: Twisted/twisted/lore/latex.py
===================================================================
--- Twisted/twisted/lore/latex.py	(revision 13178)
+++ Twisted/twisted/lore/latex.py	(working copy)
@@ -104,7 +104,7 @@
 
     baseLevel = 0
     try:
-        diaHack = not not os.popen('which dia').read()
+        diaHack = not not os.popen('which dia 2>/dev/null').read()
     except:
         # That's a no, then.
         diaHack = 0