Yes You're right, but sometimes error messages are quite good thing
So maybe there is another way to remove only this line and not the whole message..?

mediavets has provided the answer... but for the code illiterate, such as myself, this is exactly how & where to add it.

1) open you main "build.xml" in a text editor.
you will see the first four lines as such:

<?xml version="1.0" encoding="UTF-8"?>
<!-- for xml compliance -->
<!-- Generated By Kolor Panotour 1.8.0 -->
<krpano version="1.0.8.14" logkey="false" onstart="startaction">

2) add: showerrors="false" to the fourth line

<krpano version="1.0.8.14" logkey="false" onstart="startaction" showerrors="false">

3) save 

It's a little trick that I think many will find as easy... but for others have a first time looking, may not know.  For myself, the error message is not something the public audience should see.  It makes the tour look bugy, even if it has loaded improperly, often times still has functionality.  The end user will often never know except for that message.  I too wish I could edit that message...say something like "poor internet connection, loading error" or whatever.