try pinning higher version of pytest

requirements-conda-tests.txt

@@ -1,7 +1,7 @@
 coveralls>=1.3.0
 lxml>=4.3.3
 mock>=2.0.0
-pytest>=5.2.0,<=5.3.5
+pytest>=5.2.0,<=5.4.3
 pytest-cov>=2.6.1
 pytest-mock>=1.10.0
 pytest-xdist>=1.26.1