$ passa add apache-airflow
...
Traceback (most recent call last):
File "/home/hawk/.pyenv/versions/3.7.0/bin/passa", line 11, in <module>
load_entry_point('passa', 'console_scripts', 'passa')()
File "/home/hawk/git/passa/src/passa/cli/__init__.py", line 47, in main
result = f(options)
File "/home/hawk/git/passa/src/passa/cli/add.py", line 95, in main
return super(Command, self).main(options)
File "/home/hawk/git/passa/src/passa/cli/_base.py", line 73, in main
return type(self).__dict__["parsed_main"](options)
File "/home/hawk/git/passa/src/passa/cli/add.py", line 47, in main
lockfile_diff = project.difference_lockfile(prev_lockfile)
File "/home/hawk/git/passa/src/passa/internals/projects.py", line 222, in difference_lockfile
that = lockfile[section_name]._data
TypeError: 'NoneType' object is not subscriptable