PartTest::testForwardPDF tests whether the synctex integration works
and needs to create a PDF from latex sources via pdflatex.
If this is not installed the test fails, but the error message
'started' returned FALSE requires diving into the source code to debug
the problem.
By providing a more meaningful error message we make it easier for
developers and distributions to run all autotests sucessfully (short of
build-requiring a latex installation). Note that Albert does not want to
simply skip the tests in that case, so no optional build-time dependency
either.
Ref T7532