Shift exception formatting into the UI

Now we use bb.exceptions to pass pickleable traceback entries to the UI, and
the UI is free to do whatever it wants to do with this information. By
default, the log formatter for the UIs formats it with bb.exceptions.  This
also means that all exceptions should now show 3 lines of context and limit to
5 entries.

(Bitbake rev: ee48d628ee038bd72e1cd94aa75f5ccbacbcee4c)

Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/msg.py

@@ -65,9 +65,15 @@ class BBLogFormatter(logging.Formatter):
     def format(self, record):
         record.levelname = self.getLevelName(record.levelno)
         if record.levelno == self.PLAIN:
-            return record.getMessage()
+            msg = record.getMessage()
         else:
-            return logging.Formatter.format(self, record)
+            msg = logging.Formatter.format(self, record)
+
+        if hasattr(record, 'bb_exc_info'):
+            etype, value, tb = record.bb_exc_info
+            formatted = bb.exceptions.format_exception(etype, value, tb, limit=5)
+            msg += '\n' + ''.join(formatted)
+        return msg
 
 class Loggers(dict):
     def __getitem__(self, key):