coremltools is python-dependent in requires_dist

Makes the `coremltools` version explicitly dependent on the Python version in `install_requires`

src/python/setup.py

@@ -179,11 +179,12 @@ def do_not_install(require):
     ):
         install_requires.append("llvmlite == 0.31.0")
 
-    if sys.version_info[0] == 3 and sys.version_info[1] == 8:
-        # Only 4.0 betas support Python 3.8
-        install_requires.append("coremltools==4.0b3")
-    else:
-        install_requires.append("coremltools==3.3")
+    install_requires.append(
+    	# Only 4.0 betas support Python 3.8
+    	"coremltools==4.0b3; python_version >= 3.8.0',"
+    	if sys.version_info[0] == 3 and sys.version_info[1] == 8
+    	else "coremltools==3.3; python_version < 3.8.0"
+    )
 
     if sys.platform == "darwin":
         install_requires.append("tensorflow >= 2.0.0")