Add flake8 Python linting.

Pipfile

@@ -10,3 +10,4 @@ django-widget-tweaks = "*"
 
 [dev-packages]
 faker = "*"
+flake8 = "*"

Pipfile.lock

@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "837c05c254d8603c80ce3add8dfd5e9a80701a742fdd1b98568f1b664586870f"
+            "sha256": "547b11caae0d9c3ca69111553ae252eaae921249de5f2bce48bb3eb59b61d853"
         },
         "requires": {},
         "sources": [
@@ -22,7 +22,7 @@
             "version": "==1.4.1"
         },
         "djangorestframework": {
-            "version": "==3.6.3"
+            "version": "==3.6.4"
         },
         "pytz": {
             "version": "==2017.2"
@@ -32,6 +32,18 @@
         "faker": {
             "version": "==0.7.18"
         },
+        "flake8": {
+            "version": "==3.4.1"
+        },
+        "mccabe": {
+            "version": "==0.6.1"
+        },
+        "pycodestyle": {
+            "version": "==2.3.1"
+        },
+        "pyflakes": {
+            "version": "==1.5.0"
+        },
         "python-dateutil": {
             "version": "==2.6.1"
         },

gulpfile.js/tasks/lint.js

@@ -2,11 +2,26 @@ var gulp = require('gulp');
 
 var sassLint = require('gulp-sass-lint');
 var pump = require('pump');
+var spawn  = require('child_process').spawn;
 
 var watchConfig = require('../config.js').watchConfig;
 
 
-gulp.task('lint', ['lint:styles']);
+gulp.task('lint', ['lint:styles', 'lint:python']);
+
+gulp.task('lint:python', function(cb) {
+    spawn(
+        'pipenv',
+        [
+            'run',
+            'flake8',
+            '--exclude=node_modules,migrations'
+        ],
+        {
+            stdio: 'inherit'
+        }
+    ).on('exit', cb);
+});
 
 gulp.task('lint:styles', function(cb) {
     pump([

package.json

@@ -11,6 +11,7 @@
     "gulp-sass": "^3.1.0",
     "gulp-sass-glob": "^1.0.8",
     "gulp-sass-lint": "^1.3.2",
+    "gulp-spawn": "^0.4.0",
     "gulp-uglify": "^3.0.0",
     "jquery": "^3.2.1",
     "moment": "^2.18.1",