Try to load locale from plugin data folder first

src/main/java/com/gmail/nossr50/locale/LocaleLoader.java

@@ -4,10 +4,17 @@ import com.gmail.nossr50.config.Config;
 import com.gmail.nossr50.mcMMO;
 import org.bukkit.ChatColor;
 
+import java.io.IOException;
+import java.io.Reader;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.text.MessageFormat;
 import java.util.Locale;
 import java.util.MissingResourceException;
+import java.util.PropertyResourceBundle;
 import java.util.ResourceBundle;
+import java.util.logging.Level;
 
 public final class LocaleLoader {
     private static final String BUNDLE_ROOT = "com.gmail.nossr50.locale.locale";
@@ -85,7 +92,21 @@ public final class LocaleLoader {
                 locale = new Locale(myLocale[0], myLocale[1]);
             }
 
-            bundle = ResourceBundle.getBundle(BUNDLE_ROOT, locale);
+            if (locale == null) {
+                throw new IllegalStateException("Failed to parse locale string '" + Config.getInstance().getLocale() + "'");
+            }
+
+            Path localePath = Paths.get(mcMMO.getMainDirectory() + "locale_" + locale.toString() + ".properties");
+            if (Files.exists(localePath) && Files.isRegularFile(localePath)) {
+                try (Reader localeReader = Files.newBufferedReader(localePath)) {
+                    bundle = new PropertyResourceBundle(localeReader);
+                } catch (IOException e) {
+                    mcMMO.p.getLogger().log(Level.WARNING, "Failed to load locale from " + localePath, e);
+                    bundle = ResourceBundle.getBundle(BUNDLE_ROOT, locale);
+                }
+            } else {
+                bundle = ResourceBundle.getBundle(BUNDLE_ROOT, locale);
+            }
             enBundle = ResourceBundle.getBundle(BUNDLE_ROOT, Locale.US);
         }
     }