docs: Fix doc build (#1833)

* docs: Fix doc build

* docs: Use python-3.8 instead

* test: Remove pytest-asyncio form tox.ini

environment.yml

@@ -1,19 +0,0 @@
-name: py36
-dependencies:
-- pip=18.1=py36_0
-- python=3.6=0
-- setuptools=40.4.3=py36_0
-- pip:
-  - httptools>=0.0.10
-  - uvloop>=0.5.3
-  - ujson>=1.35
-  - aiofiles>=0.3.0
-  - websockets>=6.0,<7.0
-  - multidict>=4.0,<5.0
-  - sphinx==1.8.3
-  - sphinx_rtd_theme==0.4.2
-  - recommonmark==0.5.0
-  - httpx==0.11.1
-  - sphinxcontrib-asyncio>=0.2.0
-  - docutils==0.14
-  - pygments==2.3.1

readthedocs.yml

@@ -1,2 +1,9 @@
-conda:
-    file: environment.yml
+version: 2
+python:
+   version: 3.8
+   install:
+      - method: pip
+        path: .
+        extra_requirements:
+            - docs
+   system_packages: true

tox.ini

@@ -9,7 +9,6 @@ setenv =
 deps =
     coverage
     pytest==5.2.1
-    pytest-asyncio
     pytest-cov
     pytest-sanic
     pytest-sugar