AUTO-6263: requirements.txt: Add dependency version constraints based on Python version

Drop the version constraints from the dependencies listed in the
install_requires[] keyword argument to setup(). Instead, require that
"-r requirements.txt" be supplied to "pip install" and populate the file
with rules conditional on the version of Python being used. Determine
the rules for a dependency by examining the Python versions shown as
Requires and Classifiers on the documentation for its versions on PyPi.

Also, rearrange the list of dependencies in install_requires[] to be in
alphabetical order and indicate for which submodule the dependency is
for.

Author: herb-kuta-lge

requirements.txt

@@ -1,4 +1,15 @@
-websockets>=7.0
-websocket-client==0.57.0  # for dreamview
-numpy  # for evaluator
-environs
+
+# - PACKAGE >= PKG_VERSION ; python_version >= PYTHON_VERSION
+#       PKG_VERSION is the first version of PACKAGE that supports PYTHON_VERSION
+# - PACKAGE < PKG_VERSION  ; python_version < PYTHON_VERSION
+#       PKG_VERSION is the first version of PACKAGE that no longer supports
+#       PYTHON_VERSION; add entries for PYTHON_VERSION > "python_requires" of
+#       lgsvl in setup.py
+# - Keep in alphabetical order.
+environs >= 8.1.0           ; python_version >= '3.9'
+numpy < 1.20                ; python_version <  '3.7'
+numpy >= 1.20               ; python_version >= '3.7'
+websocket-client >= 0.58.0  ; python_version >= '3.8'
+websockets < 8.1            ; python_version <  '3.6.1'
+websockets >= 8.1           ; python_version >= '3.8'
+websockets >= 9.0.1         ; python_version >= '3.9'

setup.py

@@ -86,10 +86,10 @@ def get_version(git_tag):
     url="https://github.com/lgsvl/PythonAPI",
     packages=["lgsvl", "lgsvl.dreamview", "lgsvl.evaluator", "lgsvl.wise"],
     install_requires=[
-        "websockets==7.0",
-        "websocket-client==0.57.0",
-        "numpy",
-        "environs"
+        "environs",
+        "numpy",                # for evaluator
+        "websocket-client",     # for dreamview
+        "websockets"
     ],
     setup_requires=[
         "GitPython==3.1.14"