sanity.bbclass: Use pythonexception to raise real exceptions without backtraces
If the sanity code encounters a version change is doesn't understand, the current
output is unreadable and confusing for the user, particularly due to the presence
of the backtrace.
Use improved functionality in bitbake to improve this and correctly pass python
exceptions around.
[YOCTO #9291]
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
