Fix broken tests on develop about ricecooker

[AtKristijan]

tests/test_exercises.py::test_exercise_graphie_filename
E AssertionError: wrong filename for _ExerciseGraphieFile E assert 'ee76848822bf...078b6.graphie' == 'ea2269bb5cf4...6fbc7.graphie' E - ea2269bb5cf487f8d883144b9c06fbc7.graphie E + ee76848822bf710e037999e9148078b6.graphie

tests/test_files.py::test_convertible_substitles_ar_ttml
E AssertionError: conferted filename must exit E assert None

tests/test_files.py::test_convertible_substitles_noext_subtitlesformat
E AssertionError: conferted filename must exit E assert None

tests/test_thumbnails.py::TestThumbnailGeneration::test_generate_thumbnail_from_pdf
E AssertionError: expected two filenames E assert 1 == 2 E + where 1 = len(['b976c31a7ab68a97f12541d661245238.pdf'])

tests/media_utils/test_thumbnails.py::Test_pdf_thumbnail_generation::test_generates_thumbnail
E FileNotFoundError: [WinError 2] The system cannot find the file specified

tests/media_utils/test_thumbnails.py::Test_pdf_thumbnail_generation::test_generates_16_9_thumbnail
E ricecooker.utils.images.ThumbnailGenerationError: Fail on PDF C:\projects\learning_equallity\ricecooker\tests\media_utils\files\generate_thumbnail\sampl e.pdf Unable to get page count. Is poppler installed and in PATH?

Detailed errors from running the tests

[AtKristijan]

test_exercise_graphie_filename

function process_file is failing because generate_graphie_file can not find the path for the file "tests/testcontent/exercises/eb3f3bf7c317408ee90995b5bcf4f3a59606aedd"
The file is found if we use "testcontent/exercises/eb3f3bf7c317408ee90995b5bcf4f3a59606aedd"

@pytest.fixture def exercise_graphie_filename(): return "ea2269bb5cf487f8d883144b9c06fbc7.graphie"
This is wrong its not returning this graphie
Expected :ea2269bb5cf487f8d883144b9c06fbc7.graphie Actual :ee76848822bf710e037999e9148078b6.graphie

[AtKristijan]

This is for test test_convertible_substitles_ar_ttml

files.py > write_and_get_hash > return > File failed to write (corrupted).