Add GitHub Actions workflow to check black formatting

.github/workflow-scripts/check-trailing-newline

@@ -1,37 +0,0 @@
-#!/bin/bash
-
-# Verify that all text files end in a trailing newline.
-
-# Exit on first failing command.
-set -e
-
-# Exit on unset variable.
-set -u
-
-success=0
-
-function is_plaintext_file() {
-  local file="$1"
-  if [[ $file == *.svg ]]; then
-    echo ""
-    return
-  fi
-  file --brief "${file}" | grep text
-}
-
-# Split strings on newlines.
-IFS='
-'
-for file in $(git ls-files)
-do
-  if [[ -z $(is_plaintext_file "${file}") ]]; then
-    continue
-  fi
-
-  if ! [[ -z "$(tail -c 1 "${file}")" ]]; then
-    printf "File must end in a trailing newline: %s\n" "${file}" >&2
-    success=255
-  fi
-done
-
-exit "${success}"

.github/workflow-scripts/check-trailing-whitespace

@@ -1,26 +0,0 @@
-#!/bin/bash
-
-# Check for trailing whitespace at end of lines.
-
-# Exit on first failing command.
-set -e
-# Exit on unset variable.
-set -u
-
-FOUND_TRAILING_WHITESPACE=0
-
-while read -r line; do
-  if grep \
-    "\s$" \
-    --line-number \
-    --with-filename \
-    --binary-files=without-match \
-    --exclude="*.svg" \
-    --exclude="*.eps" \
-    "${line}"; then
-    echo "ERROR: Found trailing whitespace" >&2;
-    FOUND_TRAILING_WHITESPACE=1
-  fi
-done < <(git ls-files)
-
-exit "${FOUND_TRAILING_WHITESPACE}"

.github/workflows/ci.yml

@@ -81,20 +81,19 @@ jobs:
         run: |
           cd src/
           pycodestyle
-  whitespace:
+  formatting:
     runs-on: ubuntu-20.04
     steps:
       -
         name: Checkout
         uses: actions/checkout@v2
       -
-        name: Ensure there are no trailing spaces
-        run: |
-          .github/workflow-scripts/check-trailing-whitespace
-      -
-        name: Ensure all text files end with a trailing newline
-        run: |
-          .github/workflow-scripts/check-trailing-whitespace
+        name: Run black
+        uses: psf/black@stable
+        with:
+          options: "--check --diff --verbose"
+          src: "./src"
+          version: "22.1.0"
 
   tests:
     runs-on: ubuntu-20.04