make exception handling syntax consistent

Update exception handling syntax to use the modern style:
except ExcType as localvar

(Bitbake rev: dbf5f42b06bef81749b13aa99945cc1292a6676d)

Signed-off-by: Scott Garman <scott.a.garman@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/process.py

@@ -93,7 +93,7 @@ def run(cmd, input=None, log=None, **options):
 
     try:
         pipe = Popen(cmd, **options)
-    except OSError, exc:
+    except OSError as exc:
         if exc.errno == 2:
             raise NotFoundError(cmd)
         else: