Add pagedown custom css to wagtail admin.

opentech/public/utils/wagtail_hooks.py

+from django.contrib.staticfiles.templatetags.staticfiles import static
+
 from wagtail.contrib.modeladmin.options import ModelAdminGroup, ModelAdmin, modeladmin_register
+from wagtail.core import hooks
 
 from opentech.public.news.models import NewsType
 from opentech.public.people.models import PersonType
@@ -21,3 +24,10 @@ class TaxonomiesModelAdminGroup(ModelAdminGroup):
 
 
 modeladmin_register(TaxonomiesModelAdminGroup)
+
+
+@hooks.register('insert_editor_css')
+def editor_css():
+    link = '<link rel="stylesheet" href="{}">\n'
+    path = static('css/apply/wagtail_editor.css')
+    return link.format(path)

opentech/static_src/src/sass/apply/wagtail_editor.scss

+// Abstracts
+@import 'abstracts/functions';
+@import 'abstracts/mixins';
+@import 'abstracts/variables';
+
+.wmd-panel {
+}
+
+.wmd-input {
+}
+
+.wmd-preview {
+    background-color: $color--sky-blue;
+    padding: 0 10px;
+    width:  100%;
+    overflow: hidden; /* prevent collapsing margins */
+
+    p {
+        margin:  1em 0;
+    }
+
+    ul {
+        padding-left: 20px;
+
+        li {
+            list-style: outside disc;
+        }
+    }
+
+    ol {
+        padding-left: 0;
+
+        li {
+            list-style: inside decimal;
+        }
+    }
+}
+
+.wmd-button-row {
+    position: relative;
+    background-color: $color--white;
+    height: 25px;
+    padding-left: 5px;
+    padding-right: 5px;
+    padding-bottom: 5px;
+    padding-top: 10px;
+}
+
+.wmd-spacer {
+    position: absolute;
+    display: inline-block;
+    background-color: $color--mid-grey;
+    width: 1px;
+    height: 20px;
+    margin-left: 14px;
+    list-style: none;
+}
+
+.wmd-button {
+    position: absolute;
+    display: inline-block;
+    width: 20px;
+    height: 20px;
+    padding-left: 2px;
+    padding-right: 3px;
+    list-style: none;
+    cursor: pointer;
+
+    & > span {
+        display: inline-block;
+        background-image: url('./../../images/editor-buttons.png');
+        background-repeat: no-repeat;
+        background-position: 0 0;
+        width: 20px;
+        height: 20px;
+    }
+}
+
+.wmd-spacer1 {
+    left: 50px;
+}
+
+.wmd-spacer2 {
+    left: 175px;
+}
+
+.wmd-spacer3 {
+    left: 300px;
+}
+
+.wmd-prompt-background {
+    background-color: $color--black;
+}
+
+.wmd-prompt-dialog {
+    background-color: $color--light-grey;
+    padding:  .5em;
+    border: 4px solid $color--primary;
+}