PDF: Use pytest.mark.skipif for skipping tests

Instead of leaving test early if they can not run, use the
pytest.mark.skipif marked to tell the test system not to
even run the test.

This also adds to the stats, because skipped tests are
counted differently. Thus making it obvious, that some
tests did not run, because of any reason.

mediagoblin/tests/test_pdf.py

@@ -17,16 +17,15 @@
 import tempfile
 import shutil
 import os
-
+import pytest
 
 from mediagoblin.media_types.pdf.processing import (
     pdf_info, check_prerequisites, create_pdf_thumb)
 
 GOOD='mediagoblin/tests/test_submission/good.pdf'
 
+@pytest.mark.skipif("not check_prerequisites()")
 def test_pdf():
-    if not check_prerequisites():
-        return
     good_dict = {'pdf_version_major': 1, 'pdf_title': '',
         'pdf_page_size_width': 612, 'pdf_author': '',
         'pdf_keywords': '', 'pdf_pages': 10,

mediagoblin/tests/test_submission.py

@@ -20,6 +20,7 @@ sys.setdefaultencoding('utf-8')
 
 import urlparse
 import os
+import pytest
 
 from pkg_resources import resource_filename
 
@@ -128,9 +129,8 @@ class TestSubmission:
         self._setup(test_app)
         self.check_normal_upload(u'Normal upload 2', GOOD_PNG)
 
+    @pytest.mark.skipif("not pdf_check_prerequisites()")
     def test_normal_pdf(self, test_app):
-        if not pdf_check_prerequisites():
-            return
         self._setup(test_app)
         response, context = self.do_post({'title': u'Normal upload 3 (pdf)'},
                                          do_follow=True,