A temporary fix for bookbook dep

2 jobs for develop in 1 minute and 28 seconds (queued for 1 minute)
Name Stage Failure
failed
test Test
nbcourse/book.py:4: in <module>
from bookbook.latex import combine_and_convert
E ModuleNotFoundError: No module named 'bookbook'
=========================== short test summary info ============================
ERROR tests/test_nbcourse.py
ERROR tests/test_utils.py
!!!!!!!!!!!!!!!!!!! Interrupted: 2 errors during collection !!!!!!!!!!!!!!!!!!!!
============================== 2 errors in 0.38s ===============================
ERROR: Job failed: exit code 1