Add semi-transparent border around explorer menu

Fixes #2519. Fix provided by @alexgleason

CHANGELOG.txt

@@ -34,6 +34,7 @@ Changelog
  * Fix: All admin forms that could potentially include file upload fields now specify `multipart/form-data` where appropriate (Tim Heap)
  * Fix: REM units in Wagtailuserbar caused incorrect spacing (Vincent Audebert)
  * Fix: Explorer menu no longer scrolls with page content (Vincent Audebert)
+ * Fix: Border added around explorer menu to stop it blending in with StreamField block listing (Alex Gleason)
 
 
 1.4.4 (xx.xx.2016)

docs/releases/1.5.rst

@@ -63,6 +63,7 @@ Bug fixes
  * All admin forms that could potentially include file upload fields now specify ``multipart/form-data`` where appropriate (Tim Heap)
  * REM units in Wagtailuserbar caused incorrect spacing (Vincent Audebert)
  * Explorer menu no longer scrolls with page content (Vincent Audebert)
+ * Border added around explorer menu to stop it blending in with StreamField block listing (Alex Gleason)
 
 
 Upgrade considerations

wagtail/wagtailadmin/static_src/wagtailadmin/scss/components/_main-nav.scss

@@ -416,6 +416,17 @@ body.explorer-open {
             display: none;
         }
 
+        .explorer:after {
+            content: '';
+            width: calc(100% - 2px);
+            height: 100%;
+            position: absolute;
+            top: 0;
+            right: 0;
+            z-index: -1;
+            box-shadow: 0px 0px 2px rgba(255, 255, 255, 0.9);
+        }
+
         .nav-main {
             display: block;
         }