improve error if running offline and a dependency is missing

git-svn-id: https://svn.apache.org/repos/asf/maven/components/trunk@162976 13f79535-47bb-0310-9956-ffa450edef68

maven-mboot2/src/main/java/MBoot.java

@@ -9,6 +9,7 @@
 import javax.xml.parsers.SAXParserFactory;
 import java.io.File;
 import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.Serializable;
@@ -535,6 +536,11 @@ private void createToolsClassLoader()
             String dependency = (String) i.next();
 
             File f = new File( repoLocal, dependency );
+            if ( !f.exists() )
+            {
+                throw new FileNotFoundException( "Missing dependency: " + dependency + 
+                    ( !online ? "; run again online" : "; there was a problem downloading it earlier" ) );
+            }
 
             cl.addURL( f.toURL() );
         }