fixup! Add tests for so-long.el

Test `so-long-file-local-mode-function' with a custom function.
1 job for scratch/so-long in 11 minutes and 15 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #2217
test

00:11:15

 
Name Stage Failure
failed
test Test
Makefile:301: recipe for target 'so-long.elc' failed
make[2]: *** [so-long.elc] Error 1
make[2]: Leaving directory '/builds/emacs/emacs/lisp'
Makefile:324: recipe for target 'compile-main' failed
make[1]: *** [compile-main] Error 2
make[1]: Leaving directory '/builds/emacs/emacs/lisp'
Makefile:408: recipe for target 'lisp' failed
make: *** [lisp] Error 2
ERROR: Job failed: exit code 1