aconversion: Exceptions to stderr

aconversions/src/aconversion/aconversion.cpp

@@ -128,7 +128,7 @@ int main(int argc, char* argv[])
   }
   catch( AlibException & e )
   {
-      cout << e.what( ) << endl;
+      cerr << e.what( ) << endl;
       return 1;
   }