Requiring Python >=3.8 enables walrus operator (#852)

* Requiring Python >=3.8 enables walrus operator

* Update comment to be evergreen

---------

Co-authored-by: Mike Alfare <13974384+mikealfare@users.noreply.github.com>

.changes/unreleased/Fixes-20230803-102915.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Requiring Python >=3.8 enables walrus operator
+time: 2023-08-03T10:29:15.371798-06:00
+custom:
+  Author: cemsbr dbeatty10
+  Issue: "849"

setup.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python
 import sys
 
-# require python 3.7 or newer
+# require a supported version of Python
 if sys.version_info < (3, 8):
     print("Error: dbt does not support this version of Python.")
     print("Please upgrade to Python 3.8 or higher.")
@@ -91,5 +91,5 @@ def _dbt_core_version(plugin_version: str) -> str:
         "Programming Language :: Python :: 3.10",
         "Programming Language :: Python :: 3.11",
     ],
-    python_requires=">=3.7",
+    python_requires=">=3.8",
 )