code: public String getUserKeyFile() {
  	String location;
  	location = System.getProperty("X509_USER_KEY");
  	if (location != null) {
  	    return location;
  	}
  	location = getProperty("userkey");
  	if (location != null) {
  	    return location;
  	}
  	return ConfigUtil.discoverUserKeyLocation();
      }
docs: Retrieves the location of the user key file.
  It first checks the X509_USER_KEY system property. If the property
  is not set, it checks next the 'userkey' property in the current
  configuration. If that property is not set, it returns a default
  location of the user key file. The default value
  is the 'userkey.pem' file in the user's globus directory. For example:
  ${user.home}/.globus/userkey.pem.
  
  @return <code>String</code> the location of the user key file