Added new exception for IO

git-svn-id: https://dng.biozentrum.unibas.ch/svn/openstructure/trunk@1867 5a81b35b-ba03-0410-adc8-b2c5c5119f08

modules/io/src/io_exception.hh

@@ -38,6 +38,12 @@ public:
     Error(m) {}
 };
 
+class IOFileAlreadyLoadedException: public Error {
+public:
+  IOFileAlreadyLoadedException(const String& m):
+    Error(m) {}
+};
+
 }} // ns
 
 #endif