Merge pull request #4042 from ovangle:fix-4031

[bugfix] Make auto locale loading for node not mess webpack, fixes #4031, #2979, #3872

src/lib/locale/locales.js

@@ -50,13 +50,21 @@ function loadLocale(name) {
     // TODO: Find a better way to register and load all the locales in Node
     if (!locales[name] && (typeof module !== 'undefined') &&
             module && module.exports) {
+        oldLocale = globalLocale._abbr;
         try {
-            oldLocale = globalLocale._abbr;
-            require('./locale/' + name);
-            // because defineLocale currently also sets the global locale, we
-            // want to undo that for lazy loaded locales
-            getSetGlobalLocale(oldLocale);
-        } catch (e) { }
+            require('moment/locale/' + name);
+        } catch (e) {
+            // In the test environment, the external module 'moment'
+            // can't be resolved because we're running inside it.
+            // Fallback to using the old relative import
+            try {
+                require('./locale/' + name);
+            } catch (e) { }
+        }
+
+        // because defineLocale currently also sets the global locale, we
+        // want to undo that for lazy loaded locales
+        getSetGlobalLocale(oldLocale);
     }
     return locales[name];
 }