[master] Exception handling pieces refactorization

All the work lies in PATCH 1/2 and the comment is in its commit message.

Vratislav Podzimek (2): Refactor and cleanup exception handling pieces Cleanup some trailing whitespace on otherwise empty lines

pyanaconda/exception.py | 24 ++++++++--- pyanaconda/ui/__init__.py | 30 ++++++------- pyanaconda/ui/gui/__init__.py | 97 ++++++++++++++++++++++++++++--------------- pyanaconda/ui/tui/__init__.py | 23 +++++----- 4 files changed, 110 insertions(+), 64 deletions(-)