python: avoid bare 'except:' clause

python: avoid bare 'except:' clause

Exception catching statements should always match on a class name, the
most specific one possible. Rather than analyse the code to look at what
the most specific one is, this just uses the base Exception class.

docs/apibuild.py:255:9: E722 do not use bare 'except'
        except:
        ^
docs/apibuild.py:279:9: E722 do not use bare 'except'
        except:
        ^
...more...

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>