fixed error when deleting notebooks
make flake8 happy
changed test
Revert "changed test"

This reverts commit 3286bf923580498f830f7d4554bdc5066e2a7f83.
Merge pull request #233 from bpipev/diff_deleted_nb_fix

Diff deleted nb fix
fixed a typo in the test suite
Merge pull request #234 from cel4/fix_tests

fixed a typo in the test suite