For a more detailed analysis:
- the warning gets printed very late because the socket is caught in a reference cycle (self.attr = self), which itself is tied to the exception traceback
- when the socket is collected, it tries to print a ResourceWarning because it hasn't been closed explicitly (just add self.close() in the constructor to make it disappear)
- when trying to print the ResourceWarning, it probably wants to import linecache or something, and that breaks

The only remaining mystery is why there are 200 lines and not just one :-)