ext.sesstion: fix duplicate session commit

the first two lines do essentially the same as the next 8
1: D400 First line should end with '.', not 'y'
1: D205 Blank line missing between one-line summary and description
1: D208 Docstring is over-indented
4: I102 copyright year is outdated, expected 2014 but got 2013
33:1: F401 'datetime' imported but unused
36:1: F401 'current_user' imported but unused
41:1: F401 'Session' imported but unused
44: D203 Expected 1 blank line *before* class docstring, found 0
44: D200 One-line docstring should not occupy 3 lines
49: D102 Docstring missing
56: D401 First line should be imperative: 'Return', not 'Returns'
62: D401 First line should be imperative: 'Return', not 'Returns'
69: D102 Docstring missing
75: D102 Docstring missing
81: D102 Docstring missing
85: D102 Docstring missing
90: D102 Docstring missing
93: D102 Docstring missing