Issue #23731: Implement PEP 488.

The concept of .pyo files no longer exists. Now .pyc files have an
optional `opt-` tag which specifies if any extra optimizations beyond
the peepholer were applied.
diff --git a/Lib/tkinter/test/runtktests.py b/Lib/tkinter/test/runtktests.py
index ccb3755..dbe5e88 100644
--- a/Lib/tkinter/test/runtktests.py
+++ b/Lib/tkinter/test/runtktests.py
@@ -16,7 +16,7 @@
 
 def is_package(path):
     for name in os.listdir(path):
-        if name in ('__init__.py', '__init__.pyc', '__init.pyo'):
+        if name in ('__init__.py', '__init__.pyc'):
             return True
     return False