Ok, "any file" was wrong. The problem appears to be "any file in the /tmp hierarchy". That is a common destination for downloading and unpacking stuff, including by software that displays HTML by reverting to the system browser.
The error message then is
File not found
Firefox can’t find the file at /tmp/test-results/index.html.
Check the file name for capitalization or other typing errors.
Check to see if the file was moved, renamed or deleted.
Ok, "any file" was wrong. The problem appears to be "any file in the /tmp hierarchy". That is a common destination for downloading and unpacking stuff, including by software that displays HTML by reverting to the system browser.
The error message then is
File not found
Firefox can’t find the file at /tmp/test- results/ index.html.
Check the file name for capitalization or other typing errors.
Check to see if the file was moved, renamed or deleted.