`install_e2e` fails because `werkzeug` version is too new
Job #428742189 failed for bcef904f:
File "/builds/meltano/meltano/venv/lib/python3.6/site-packages/flask_security/core.py", line 18, in <module>
from flask_babelex import Domain
File "/builds/meltano/meltano/venv/lib/python3.6/site-packages/flask_babelex/__init__.py", line 23, in <module>
from werkzeug import ImmutableDict
ImportError: cannot import name 'ImmutableDict'