Set up basic pre-commits

* black (source code formatting)
* syntax validation
* basic flake8 checks

Add an entry point to enable pre-commits if the package is installed
in a dials environment.

.pre-commit-config.yaml

@@ -0,0 +1,16 @@
+repos:
+
+# Automatic source code formatting
+- repo: https://github.com/ambv/black
+  rev: stable
+  hooks:
+  - id: black
+    args: [--safe, --quiet]
+
+# Syntax check and some basic flake8
+- repo: https://github.com/pre-commit/pre-commit-hooks
+  rev: v2.0.0
+  hooks:
+  - id: check-ast
+  - id: flake8
+    args: ['--max-line-length=88', '--select=W291,W292,W293,F401']

setup.py

@@ -31,5 +31,6 @@
         "Operating System :: OS Independent",
         "Topic :: Software Development :: Libraries :: Python Modules",
     ],
+    entry_points={"libtbx.precommit": ["ispyb = ispyb"]},
     project_urls={"Documentation": "https://ispyb.readthedocs.io"},
 )