ImportError: No module named 'flask.exthook'

Hello ! I ran into an error while running superset db upgrade :

File "/usr/local/bin/superset", line 9, in <module>
    from flask.exthook import ExtDeprecationWarning
ImportError: No module named 'flask.exthook'

For what I can see, superset uses (or can use) flask==1.0 (https://github.com/apache/incubator-superset/blob/master/setup.py#L58) that no longer has a exthook module (https://github.com/pallets/flask/releases/tag/1.0). This causes a ImportError on superset here : https://github.com/apache/incubator-superset/blob/master/superset/bin/superset#L9

When I install flask==0.12.2 before I install superset I no longer have the Error.

Maybe flask<1.0.0 would work better? Or do you think I may be doing something wrong ?

Make sure these boxes are checked before submitting your issue - thank you!

• I have checked the superset logs for python stacktraces and included it here as text if any
• I have reproduced the issue with at least the latest released version of superset
• I have checked the issue tracker for the same issue and I haven’t found one similar

Superset version

0.25.2

Expected results

There should be no error

Actual results

ImportError is raised

Steps to reproduce

pip install superset==0.25.2 (by the way, at this point we get a warning flask-appbuilder 1.10.0 has requirement Flask<0.12.99,>=0.12.1, but you'll have flask 1.0 which is incompatible.) pip freeze

[xrmx]

You should probably open a PR fixing the issue 😃

[mistercrunch]

Ooops, my bad, fixing in 0.25.4 (pushing this out now)