bitbake: Remove custom exception backtrace formatting

Removes the code in bitbake to show custom backtrace formatting for
exceptions. In particular, the bitbake exception code prints function
arguments, which while helpful is a security problem when passwords and
other secrets can be passed as function arguments.

As it turns out, the handling of the custom serialized exception stack
frames was pretty much made obsolete by d7db75020ed ("event/msg: Pass
formatted exceptions"), which changed the events to pass a preformatted
stacktrack list of strings, but the passing of the serialized data was
never removed.

Change all the code to use the python traceback API to format exceptions
instead of the custom code; conveniently traceback.format_exception()
also returns a list of stack trace strings, so it can be used as a drop
in replacement for bb.exception.format_exception()

(Bitbake rev: 1f7889c2f5e192fb108b51883aac8685ccb187f2)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>

bitbake/lib/bb/event.py

@@ -19,7 +19,6 @@ import sys
 import threading
 import traceback
 
-import bb.exceptions
 import bb.utils
 
 # This is the pid for which we should generate the event. This is set when
@@ -759,13 +758,7 @@ class LogHandler(logging.Handler):
 
     def emit(self, record):
         if record.exc_info:
-            etype, value, tb = record.exc_info
-            if hasattr(tb, 'tb_next'):
-                tb = list(bb.exceptions.extract_traceback(tb, context=3))
-            # Need to turn the value into something the logging system can pickle
-            record.bb_exc_info = (etype, value, tb)
-            record.bb_exc_formatted = bb.exceptions.format_exception(etype, value, tb, limit=5)
-            value = str(value)
+            record.bb_exc_formatted = traceback.format_exception(*record.exc_info)
             record.exc_info = None
         fire(record, None)