EPUB tests using installed code

[Gavin Smith]

On Wed, Jul 27, 2022 at 10:45:24PM +0200, Patrice Dumas wrote:
> I agree.  I do not think that we want to change the init files directory
> search path.  But, maybe the init files that are used in texi2any.pl
> should be in a different directory and be considered 'internal' and not
> regular init files, and be loaded by a different function than
> locate_and_load_init_file().  This could be somewhat confusing, though,
> that --init-file and loading from texi2any.pl is not the same file.
> Maybe we should just document it clearly.

I was getting test failures for two of the EPUB tests under tp/tests,
because they were using the installed modules.  Even after I ran
"make install", the tests still failed, because the init files had moved
from init/ to ext/.  It was only after I deleted the left-over files in
init/ that the tests passed.

If EPUB is part of the test suite, then it must not use code from installed
locations when the test suite runs.  If that means changing the search
path then that is what we must do.

Often, people believe there is something wrong with the program
if "make check" fails.  This might especially be the case in the future
if test results change between official releases.