bitbake: bitbake: fix wrong usage of format_exc

First parameter of traceback.format_exc is a 'limit' - a number
of stracktraces to format.

Passing exception object to format_exc is incorrect, but it works in
Python 2 as this code from traceback module works:
    while tb is not None and (limit is None or n < limit):
Comparing integer counter n with the exception object in Python 2
always results in True. However, in Python 3 it throws exception:
    TypeError: unorderable types: int() < <Exception type>()

As format_exc is used in except block of handling another
exception this can cause hard to find and debug bugs.

(Bitbake rev: a9509949d7e2adba6e3cd89f97daa19a955855b5)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/ui/uievent.py

@@ -116,7 +116,7 @@ class BBUIEventQueue:
                 self.server.handle_request()
             except Exception as e:
                 import traceback
-                logger.error("BBUIEventQueue.startCallbackHandler: Exception while trying to handle request: %s\n%s" % (e, traceback.format_exc(e)))
+                logger.error("BBUIEventQueue.startCallbackHandler: Exception while trying to handle request: %s\n%s" % (e, traceback.format_exc()))
 
         self.server.server_close()