Test coverage for ZODB backend is below 100%

[stevepiercy]

After generating a project using ZODB on the backend, then running tests with coverage via pytest --cov reveals test coverage is only at 42%.

Name                           Stmts   Miss  Cover
--------------------------------------------------
zodb_demo/__init__.py             16     11    31%
zodb_demo/models/__init__.py       8      4    50%
zodb_demo/pshell.py                6      6     0%
zodb_demo/routes.py                2      2     0%
zodb_demo/views/__init__.py        0      0   100%
zodb_demo/views/default.py         4      0   100%
zodb_demo/views/notfound.py        4      0   100%
--------------------------------------------------
TOTAL                             40     23    42%

See also #79.