Replace bash scripts with python scripts

pre-commit.d/black.py

@@ -0,0 +1,43 @@
+#!/usr/bin/env python
+
+import os
+import subprocess
+import sys
+
+from shutil import which
+
+if not os.getenv("VIRTUAL_ENV"):
+    sys.exit("Ensure your virtualenv is activated.")
+
+file_extensions = (".py",)
+line_length = os.getenv("BLACK_LINE_LENGTH", 88)
+black = os.getenv("BLACK_BIN", "black")
+options = ["-l", str(line_length),]
+
+if not which(black):
+    sys.exit("Black binary not found")
+
+diff = subprocess.check_output(
+    ["git", "diff", "--cached", "--name-only", "--diff-filter", "ACM"],
+    universal_newlines=True
+)
+
+python_files = [
+    item for item in diff.splitlines() if item.endswith(file_extensions)
+]
+
+if not python_files:
+    sys.exit(0)
+
+try:
+    output = subprocess.check_output(
+        [black, *options, *python_files],
+        universal_newlines=True,
+        stderr=subprocess.STDOUT
+    )
+except subprocess.CalledProcessError as e:
+    print("Formatting was unsuccessful:")
+    sys.exit(e.stdout)
+
+subprocess.run(["git", "add", "-u", *python_files])
+sys.exit(0)