bump exdown requirement and use the new encodimg parameter

PySDM_tests/devops_tests/test_readme_code.py

@@ -1,10 +1,9 @@
 import exdown
 import pathlib
-import pytest
-import sys
 
 
-test_readme = pytest.mark.skipif("sys.getfilesystemencoding() != 'utf-8'")(exdown.pytests(
+test_readme = exdown.pytests(
     pathlib.Path(__file__).parent.parent.parent.joinpath("README.md").absolute(),
-    syntax_filter="Python"
-))
+    syntax_filter="Python",
+    encoding='utf8'
+)

requirements.txt

@@ -2,7 +2,7 @@
 matplotlib>=3.2.2
 ghapi
 pytest
-exdown
+exdown>=0.8.8
 
 # note: if cloning both PySDM and PySDM examples, consider "pip install -e"
 git+git://github.com/atmos-cloud-sim-uj/PySDM-examples