Fix tox config

Signed-off-by: Bernát Gábor <bgabor8@bloomberg.net>

Author: gaborbernat

tox.ini

@@ -23,7 +23,7 @@ extras =
     testing
 pass_env =
     DIFF_AGAINST
-    PYTES_*
+    PYTEST_*
 set_env =
     COVERAGE_FILE = {work_dir}/.coverage.{env_name}
     COVERAGE_PROCESS_START = {tox_root}/pyproject.toml