refactor for using with python3

[Reimar Bauer]

we have to refactor all python2 code for alternative usage on python3

https://docs.python.org/3/howto/pyporting.html

[Joern Ungermann]

A first step would be to fix the py3kwarn outputs that do not hurt us at all. For example to adapt the new Exception syntax etc. A second step would use from __future__ directives, where we should decide, which to adopt. I hope that no further tools are needed, propose to rewrite the code not to use any further directives, respectively.

[Reimar Bauer]

Fix try/except syntax to new style.

See issue #176

→ <<cset 8a4285106334>>

[Reimar Bauer]

Reduce needless usage of keys() function.

See issue #176.

→ <<cset 77175f177ea1>>

[Reimar Bauer]

Merged in ReimarBauer/mss/py3 (pull request #342)

refactoring for using with python3, fixes #176

Approved-by: Joern Ungermann [e-mail]

→ <<cset 0108ab5f44bf>>