tests: drop py2 support from `f` utility

tests: drop py2 support from `f` utility

--- a/tests/f	Tue Jan 03 23:47:29 2023 -0500
+++ b/tests/f	Tue Jan 03 23:49:05 2023 -0500
@@ -32,17 +32,10 @@
 import re
 import sys
 
-# Python 3 adapters
-ispy3 = sys.version_info[0] >= 3
-if ispy3:
 
-    def iterbytes(s):
-        for i in range(len(s)):
-            yield s[i : i + 1]
-
-
-else:
-    iterbytes = iter
+def iterbytes(s):
+    for i in range(len(s)):
+        yield s[i : i + 1]
 
 
 def visit(opts, filenames, outfile):