The quart pin is required to fix an attribute error which otherwise
occurs during startup. Hence, this should be a good qualifier to know
when it's safe to upgrade.
Note that this is not a problem in Quart, but in flask-WTForms. But
downgrading flask-wtforms does not help [1], so we don't revert that
uprade.
```
AttributeError: module 'quart.json' has no attribute 'JSONEncoder'
```
[1]: https://github.com/pallets/quart/issues/163
This is needed because jinja2 had an update which caused the portal to
not work at all:
```
ImportError: cannot import name 'escape' from 'jinja2'
```
Quart needed updating for that.
This update required a lot of typefixes. Apparently, the "canned"
responses (like redirect) are now plain werkzeug responses, while
quart.Response does not inherit from werkzeug.Response (otherwise, we
could've changed the type annotations to werkzeug.Response everywhere,
but that doesn't work because a quart.Response is not a
werkzeug.Response).
P.S.: This time, I *did* check that avatar uploads don't break (see
b007afc).
wtforms 3.0 is incompatible with our code. A separate issue will be
filed to address the incompatibilities, but this should be enough to get
working images out of it.
With 3.x, we're seeing:
```
File "/home/horazont/Projects/python/snikket-web-portal/snikket_web/main.py", line 35, in LoginForm
address = wtforms.TextField(
AttributeError: module 'wtforms' has no attribute 'TextField'
```
and the portal fails to start.
This reverts commit 486596f89f.
It was discovered that multipart/form-data forms do not work
correctly with Quart 0.15. The upgrade to Quart 0.15 was rushed
and not tested correctly, which I apologize for.
See-Also: https://github.com/pgjones/quart/issues/126
snikket_web can now be fully configured via the environment alone,
no extra files needed. It is still supported to inject a python
file to generate environment variables though, which may be
useful for generating and reloading a secret key.
