Include source of duplicate path

This simple addition to the error message helps to track down JARs
supplying identically named resources into a java_binary target.

src/com/facebook/buck/java/JarDirectoryStep.java

diff --git a/src/com/facebook/buck/java/JarDirectoryStep.java b/src/com/facebook/buck/java/JarDirectoryStep.java
index 4c6894a..4115ae4 100644
--- a/src/com/facebook/buck/java/JarDirectoryStep.java
+++ b/src/com/facebook/buck/java/JarDirectoryStep.java
@@ -50,10 +50,25 @@
 import java.util.jar.Manifest;
 import java.util.logging.Level;
 import java.util.zip.ZipEntry;
+import java.util.zip.ZipException;
 import java.util.zip.ZipFile;
 
 import javax.annotation.Nullable;
 
+import com.facebook.buck.step.ExecutionContext;
+import com.facebook.buck.step.Step;
+import com.facebook.buck.util.DirectoryTraversal;
+import com.facebook.buck.util.ProjectFilesystem;
+import com.google.common.base.Joiner;
+import com.google.common.base.Preconditions;
+import com.google.common.base.Throwables;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Sets;
+import com.google.common.io.ByteStreams;
+import com.google.common.io.Closeables;
+import com.google.common.io.Closer;
+import com.google.common.io.Files;
+
 /**
  * Creates a JAR file from a collection of directories/ZIP/JAR files.
  */
@@ -218,7 +233,13 @@
 
       ZipEntry newEntry = new ZipEntry(entry);
       newEntry.setCompressedSize(-1);
-      jar.putNextEntry(newEntry);
+      try {
+        jar.putNextEntry(newEntry);
+      } catch (ZipException ze) {
+        throw new ZipException(String.format(
+          "%s from %s",
+          ze.getMessage(), file.getPath()));
+      }
       InputStream inputStream = zip.getInputStream(entry);
       ByteStreams.copy(inputStream, jar);
       jar.closeEntry();