Try debugging CI/ubuntu-20.04 integration tests..

Does restoring the "charset_normalizer < 3" pin make the tests pass?

setup.py

@@ -147,6 +147,13 @@ install_requires = [
     # for pid-file support
     "psutil",
     "filelock",
+
+    # treq needs requests, requests needs charset_normalizer,
+    # charset_normalizer breaks PyInstaller
+    # (https://github.com/Ousret/charset_normalizer/issues/253). So work around
+    # this by using a lower version number. Once upstream issue is fixed, or
+    # requests drops charset_normalizer, this can go away.
+    "charset_normalizer < 3",
 ]
 
 setup_requires = [