Heroku failed to deploy flask

according to the code of Dog Book, the program push to heroku master, was successfully run as a result of heroku run python flasky.py deploy failure
error report is as follows:
File "/ app/.heroku/python/lib/python3.6/site-packages/alembic/script/base.py", line 334, in _ upgrade_revs

revs = list(revs)

File "/ app/.heroku/python/lib/python3.6/site-packages/alembic/script/revision.py", line 652, in _ iterate_revisions

uppers = util.dedupe_tuple(self.get_revisions(upper))

File "/ app/.heroku/python/lib/python3.6/site-packages/alembic/script/revision.py", line 300, in get_revisions

resolved_id, branch_label = self._resolve_revision_number(id_)

File "/ app/.heroku/python/lib/python3.6/site-packages/alembic/script/revision.py", line 433, in _ resolve_revision_number

self._revision_map

File "/ app/.heroku/python/lib/python3.6/site-packages/alembic/util/langhelpers.py", line 240, in get

obj.__dict__[self.__name__] = result = self.fget(obj)

File "/ app/.heroku/python/lib/python3.6/site-packages/alembic/script/revision.py", line 121, in _ revision_map

for revision in self._generator():

File "/ app/.heroku/python/lib/python3.6/site-packages/alembic/script/base.py", line 90, in _ load_revisions

for file_ in os.listdir(vers):

FileNotFoundError: [Errno 2] No such file or directory:"/ app/migrations/versions"
only truncated part, too long, ask for advice

Mar.03,2021
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