Pin to graphene < 3.0

[simonw]

I tried running the test suite against the beta of Graphene 3.0 and it broke, a lot:

(datasette-graphql) datasette-graphql % pip install graphene==v3.0.0b7
Collecting graphene==v3.0.0b7
  Downloading graphene-3.0b7-py2.py3-none-any.whl (108 kB)
     |████████████████████████████████| 108 kB 2.5 MB/s 
Collecting graphql-relay<4,>=3.0
  Downloading graphql_relay-3.0.0-py3-none-any.whl (15 kB)
Collecting aniso8601<9,>=8
  Downloading aniso8601-8.1.1-py2.py3-none-any.whl (44 kB)
     |████████████████████████████████| 44 kB 3.3 MB/s 
Collecting graphql-core<4,>=3.1.2
  Downloading graphql_core-3.1.3-py3-none-any.whl (186 kB)
     |████████████████████████████████| 186 kB 2.4 MB/s 
Installing collected packages: graphql-core, graphql-relay, aniso8601, graphene
...
Successfully installed aniso8601-8.1.1 graphene-3.0b7 graphql-core-3.1.3 graphql-relay-3.0.0
(datasette-graphql) datasette-graphql % pytest
============================================================================================== test session starts ==============================================================================================
platform darwin -- Python 3.8.2, pytest-6.2.2, py-1.10.0, pluggy-0.13.1
rootdir: /Users/simon/Dropbox/Development/datasette-graphql
plugins: asyncio-0.14.0
collected 0 items / 6 errors                                                                                                                                                                                    

==================================================================================================== ERRORS =====================================================================================================
______________________________________________________________________________________ ERROR collecting tests/test_docs.py ______________________________________________________________________________________
ImportError while importing test module '/Users/simon/Dropbox/Development/datasette-graphql/tests/test_docs.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
../../../.pyenv/versions/3.8.2/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_docs.py:5: in <module>
    from .test_graphql import graphql_re, variables_re
tests/test_graphql.py:1: in <module>
    from datasette.app import Datasette
../../../.local/share/virtualenvs/datasette-graphql-n1OSJCS8/lib/python3.8/site-packages/datasette/app.py:30: in <module>
    from .views.base import DatasetteError, ureg
../../../.local/share/virtualenvs/datasette-graphql-n1OSJCS8/lib/python3.8/site-packages/datasette/views/base.py:12: in <module>
    from datasette.plugins import pm
../../../.local/share/virtualenvs/datasette-graphql-n1OSJCS8/lib/python3.8/site-packages/datasette/plugins.py:24: in <module>
    pm.load_setuptools_entrypoints("datasette")
../../../.pyenv/versions/3.8.2/lib/python3.8/importlib/metadata.py:77: in load
    module = import_module(match.group('module'))
../../../.pyenv/versions/3.8.2/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
datasette_graphql/__init__.py:5: in <module>
    from graphql.execution.executors.asyncio import AsyncioExecutor
E   ModuleNotFoundError: No module named 'graphql.execution.executors'
____________________________________________________________________________________ ERROR collecting tests/test_graphql.py _____________________________________________________________________________________