A temporary fix for bookbook dep

3 jobs for master in 2 minutes and 43 seconds (queued for 3 seconds)
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 !!!!!!!!!!!!!!!!!!!!
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ERROR: Job failed: exit code 1