added python version checker. starting with 3.8; but we can lower if we confirm that lower works.

linkulator.py

@@ -438,6 +438,13 @@ def signal_handler(sig, frame):
 
 def main():
     """main function - handles argument parsing and calls menu system"""
+
+    low_py_ver = 3.8
+    py_ver = str(sys.version_info[0]) + "." + str(sys.version_info[1])
+    py_ver = float(py_ver)
+    if py_ver < low_py_ver:
+        raise Exception("Must be using Python " + str(low_py_ver) + " or higher.  Instead you're using " + str(py_ver))
+
     signal.signal(signal.SIGINT, signal_handler)
     args = sys.argv[1:]
     config.init()