[Fixes GeoNode#5719] Add pre-commit and black

Author: frafra

.pre-commit-config.yaml

@@ -0,0 +1,14 @@
+# See https://pre-commit.com for more information
+# See https://pre-commit.com/hooks.html for more hooks
+repos:
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v2.5.0
+    hooks:
+    -   id: trailing-whitespace
+    -   id: end-of-file-fixer
+    -   id: check-yaml
+    -   id: check-added-large-files
+-   repo: https://github.com/psf/black
+    rev: 19.10b0
+    hooks:
+    -   id: black

pyproject.toml

@@ -0,0 +1,15 @@
+[tool.black]
+line-length = 120
+target-version = 'py35'
+exclude = '''
+/(
+    geonode/.*/migrations/.*
+  | geonode/.*/settings.py
+  | management
+  | scripts
+  | docs
+  | static
+  | migrations
+  | node_modules
+)/
+'''

requirements_dev.txt

@@ -1 +1,2 @@
-ipdb
+ipdb
+pre-commit