Update minimum Python version requirement from 3.9 to 3.8 for compatibility.

Author: LeiWang1999

python/tvm/base.py

@@ -26,8 +26,8 @@
 # ----------------------------
 # Python3 version.
 # ----------------------------
-if not (sys.version_info[0] >= 3 and sys.version_info[1] >= 9):
-    PY3STATEMENT = "The minimal Python requirement is Python 3.9"
+if not (sys.version_info[0] >= 3 and sys.version_info[1] >= 8):
+    PY3STATEMENT = "The minimal Python requirement is Python 3.8"
     raise Exception(PY3STATEMENT)
 
 # ----------------------------