Add Stylelint to gulp and CI

.stylelintrc

@@ -0,0 +1,38 @@
+{
+  "rules": {
+    "color-no-invalid-hex": true,
+    "font-family-no-duplicate-names": true,
+    "function-name-case": "lower",
+    "function-url-no-scheme-relative": true,
+    "number-no-trailing-zeros": true,
+    "length-zero-no-unit": true,
+    "unit-case": "lower",
+    "unit-no-unknown": true,
+    "value-keyword-case": "lower",
+    "property-case": "lower",
+    "property-no-unknown": true,
+    "keyframe-declaration-no-important": true,
+    "declaration-no-important": true,
+    "declaration-block-no-duplicate-properties": true,
+    "declaration-block-no-ignored-properties": true,
+    "declaration-block-no-shorthand-property-overrides": true,
+    "declaration-block-single-line-max-declarations": 1,
+    "declaration-block-trailing-semicolon": "always",
+    "block-no-empty": true,
+    "selector-no-empty": true,
+    "selector-pseudo-class-no-unknown": true,
+    "selector-pseudo-element-no-unknown": true,
+    "selector-pseudo-element-case": "lower",
+    "selector-type-case": "lower",
+    "selector-type-no-unknown": true,
+    "selector-max-empty-lines": 0,
+    "media-feature-name-case": "lower",
+    "media-feature-name-no-unknown": true,
+    "media-feature-no-missing-punctuation": true,
+    "comment-no-empty": true,
+    "no-duplicate-selectors": true,
+    "no-invalid-double-slash-comments": true,
+    "no-unknown-animations": true,
+    "no-extra-semicolons": true
+  }
+}

circle.yml

@@ -33,6 +33,7 @@ test:
   pre:
     - mkdir -p "$CIRCLE_TEST_REPORTS/django"
   override:
+    - gulp css:lint
     - gulp js:lint
     - gulp js:test
     - make test-image

gulpfile.js

@@ -9,6 +9,7 @@ const del = require('del');
 const karma = require('karma');
 const eslint = require('gulp-eslint');
 const watch = require('gulp-watch');
+const gulpStylelint = require('gulp-stylelint');
 
 const lintPaths = [
     'media/js/**/*.js',
@@ -39,6 +40,16 @@ gulp.task('js:lint', () => {
         .pipe(eslint.failAfterError());
 });
 
+
+gulp.task('css:lint', function lintCssTask() {
+    return gulp.src('media/css/**/*.scss')
+        .pipe(gulpStylelint({
+            reporters: [
+                {formatter: 'string', console: true}
+            ]
+        }));
+});
+
 gulp.task('static:clean', () => {
     return del(['static/**', '!static', '!static/.gitignore']);
 });