Fix minor Python syntax errors

The installation fails because of these:

	TabError: inconsistent use of tabs and spaces in indentation
	SyntaxError: Missing parentheses in call to 'print'
Fix minor Python styling issues

* Do not use sapces inside parenthesis
* make indend PEP8
* empty lines should not contain whitespaces
Merge pull request #2138 from owncloud/cleanup_shell_integration_nautilus

Cleanup and make python3 compatible shell integration nautilus