bitbake: knotty: Improve exception error message

bitbake: knotty: Improve exception error message

Instead of:
"""
can only concatenate tuple (not "int") to tuple
"""
we now see:

"""
Traceback (most recent call last):
  File "/media/build1/poky/bitbake/lib/bb/ui/knotty.py", line 324, in main
    termfilter.updateFooter()
  File "/media/build1/poky/bitbake/lib/bb/ui/knotty.py", line 210, in updateFooter
    lines = 1 + int(len(content) / (self.columns + 1))
TypeError: can only concatenate tuple (not "int") to tuple
"""

which makes tacking down and fixing the problem much easier.

Also ensure we set an error exit code.

(Bitbake rev: d965bcae6cfd268406a3bd1ef77c5bb6c6e1c6d7)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>