Limit pyserial version to <4

setup.py

@@ -66,7 +66,7 @@
     # your project is installed. For an analysis of "install_requires" vs pip's
     # requirements files see:
     # https://packaging.python.org/en/latest/requirements.html
-    install_requires=["pyserial>=3"],
+    install_requires=["pyserial>=3,<4"],
     # List additional groups of dependencies here (e.g. development
     # dependencies). You can install these using the following syntax,
     # for example: