update black verison

Author: MarcoGorelli

.pre-commit-config.yaml

@@ -1,6 +1,6 @@
 repos:
 -   repo: https://github.com/python/black
-    rev: 19.10b0
+    rev: 20.8b1
     hooks:
     -   id: black
         language_version: python3

doc/source/development/contributing.rst

@@ -720,7 +720,7 @@ submitting code to run the check yourself::
 to auto-format your code. Additionally, many editors have plugins that will
 apply ``black`` as you edit files.
 
-You should use a ``black`` version >= 19.10b0 as previous versions are not compatible
+You should use a ``black`` version 20.8b1 as previous versions are not compatible
 with the pandas codebase.
 
 If you wish to run these checks automatically, we encourage you to use

environment.yml

@@ -15,7 +15,7 @@ dependencies:
   - cython>=0.29.21
 
   # code checks
-  - black=19.10b0
+  - black=20.8b1
   - cpplint
   - flake8<3.8.0  # temporary pin, GH#34150
   - flake8-comprehensions>=3.1.0  # used by flake8, linting of unnecessary comprehensions