I wish I could be more helpful than to just pipe up with a "this bug affects me, too," note, but wanted to poke this bug report since it's been dormant for 14 months.
With Python 3.8.2 I tried using the pgpdump module (version 1.5, installed from pip) on Windows 10 and wanted to step through how it worked. As soon as I enabled the debugger in IDLE it stopped working, throwing a very similar stack trace. Here's the MWE:

>>> import pgpdump
>>> <turn on debugger, Locals is checked by default>
[DEBUG ON]
>>> pgpdump.BinaryData(b'')
<focus auto-switches to debug window>
<click Step button>
Traceback (most recent call last):
  File "<pyshell#1>", line 1, in <module>
    pgpdump.BinaryData(b'')
  File "C:\Python38\lib\site-packages\pgpdump\data.py", line 13, in __init__
    if not data:
  File "C:\Python38\lib\site-packages\pgpdump\data.py", line 13, in __init__
    if not data:
  File "C:\Python38\lib\bdb.py", line 88, in trace_dispatch
    return self.dispatch_line(frame)
  File "C:\Python38\lib\bdb.py", line 112, in dispatch_line
    self.user_line(frame)
  File "C:\Python38\lib\idlelib\debugger.py", line 24, in user_line
    self.gui.interaction(message, frame)
AttributeError: 'BinaryData' object has no attribute 'length'

This error only occurs when the Locals checkbox in the debugging window is checked - it runs as expected as long as Locals is unchecked (this minimum [not]working example throws a "pgpdump.utils.PgpdumpException: no data to parse" error, as it should). A longer example with actual data will run for several steps while Locals is unchecked, but fails with the first Step once Locals is checked. A side note is that the specific error here is that the class BinaryData is being asked about it's 'length', rather than the OP's error of _ModuleLock not having a 'name'
Is there anything else I can do to help fix this, given that I'm not familiar with programming bdb or the IDLE debugger GUI?