from __future__ import print_function

import sys

class DelWrapper(object):
	"""
	Wrap a dict and print the stack with a del operation occurs on the
	wrapped object.
	"""
	# save modules not in the globals to avoid issues if they gets cleaned up
	traceback = __import__('traceback')
	inspect = __import__('inspect')

	def __init__(self, wrapped):
		self.wrapped = wrapped

	def __getattr__(self, name):
		return getattr(self.wrapped, name)

	def __delitem__(self, item):
		if item.startswith('encodings.'):
			msg = "*** deletion of {item} detected ***".format(**vars())
			print(msg, file=sys.stderr)
			frame = self.inspect.currentframe().f_back
			self.traceback.print_stack(frame)
			print("*" * len(msg))
			# suppress the deletion
			return
		del self.wrapped[item]

	def __enter__(self):
		sys.modules = self

	def __exit__(self, type, val, tb):
		sys.modules = self.wrapped

with DelWrapper(sys.modules):
	b'x'.decode('utf-8')
	del __import__('locale').encodings
	del sys.modules['encodings.utf_8'], sys.modules['encodings']
	b'x'.decode('utf-8')