This reverts commit 620b2cd6e.
Contributors setting up a new development environment were getting
errors like this:
```
++ dirname tools/do-destroy-rebuild-database
[...]
+ ./manage.py purge_queue --all
Traceback (most recent call last):
[...]
File "/home/zulipdev/zulip/zproject/legacy_urls.py", line 3, in <module>
import zerver.views.streams
File "/home/zulipdev/zulip/zerver/views/streams.py", line 187, in <module>
method_kwarg_pairs: List[FuncKwargPair]) -> HttpResponse:
File "/usr/lib/python3.5/typing.py", line 1025, in __getitem__
tvars = _type_vars(params)
[...]
File "/usr/lib/python3.5/typing.py", line 277, in _get_type_vars
for t in types:
TypeError: 'ellipsis' object is not iterable
```
The issue appears to be that we're using the `typing` module from the
3.5 stdlib, rather than the `typing=3.6.2` in our requirements files,
and that doesn't understand the `Callable[..., HttpResponse]` that
appears in the definition of `FuncKwargPair`.
Revert for now to get provision working again; at least one person
reports that reverting this sufficed. We'll need to do more testing
before putting this change back in.