By the way, Python allows also to set an environment with a name containing "=", whereas getenv/setenv/unsetenv doesn't.

$ env -i python -c 'import pprint, posix, os; os.environ["a="]="1"; print(os.environ); posix.unsetenv("a=")'

environ({'a=': '1'})
Traceback (most recent call last):
  File "<string>", line 1, in <module>
OSError: [Errno 22] Invalid argument