https://github.com/jruby/jruby/issues/1248#issuecomment-29111251

0001-Modify-LoadService.splitJarUrl-to-unescape-URLs.patch

From 12b3f8764cddf147ed774078add9dd544832e685 Mon Sep 17 00:00:00 2001
From: Mark Triggs <mark@dishevelled.net>
Date: Sat, 23 Nov 2013 09:27:48 +1100
Subject: [PATCH] Modify LoadService.splitJarUrl to unescape URLs

Resolves the issue with loading 'yaml' described in #1248
---
 .../main/java/org/jruby/runtime/load/LoadService.java  |   16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/core/src/main/java/org/jruby/runtime/load/LoadService.java b/core/src/main/java/org/jruby/runtime/load/LoadService.java
index a3c02f2..4235b59 100644
--- a/core/src/main/java/org/jruby/runtime/load/LoadService.java
+++ b/core/src/main/java/org/jruby/runtime/load/LoadService.java
@@ -1392,13 +1392,21 @@ public class LoadService {
     }
     
     private String[] splitJarUrl(String loadPathEntry) {
-        int idx = loadPathEntry.indexOf("!");
+        String unescaped = loadPathEntry;
+
+        try {
+            unescaped = new URI(loadPathEntry).getSchemeSpecificPart();
+        } catch (URISyntaxException e) {
+            // Fall back to using the original string
+        }
+
+        int idx = unescaped.indexOf("!");
         if (idx == -1) {
-            return new String[]{loadPathEntry, ""};
+            return new String[]{unescaped, ""};
         }
 
-        String filename = loadPathEntry.substring(0, idx);
-        String entry = idx + 2 < loadPathEntry.length() ? loadPathEntry.substring(idx + 2) : "";
+        String filename = unescaped.substring(0, idx);
+        String entry = idx + 2 < unescaped.length() ? unescaped.substring(idx + 2) : "";
 
         if(filename.startsWith("jar:")) {
             filename = filename.substring(4);
-- 
1.7.10.4