ddd + pydb : python file in /usr/bin : not in executable format

[themusicgod1]

to reproduce:

create a somewhat obviously python test file (with or without .py):
example

themusicgod1@Hedy:~/foob$ cat m_test.py
#!/bin/python
x = 1
if x == 1:
    # indented four spaces
    print ("x is 1.")

copy this file to /usr/bin

themusicgod1@Hedy:~/foob$ which m_test.py
/usr/bin/m_test.py

cd into the directory of your *local* file

themusicgod1@Hedy:~$ cd foob
themusicgod1@Hedy:~/foob$ ls
mnemosyne m_test.py

run ddd on m_test.py

This Works. So far so good?

now change into another directory. What should happen here is that because m_test.py is still in the system path, ddd/pydb should still see it, and start a debugging session with it.
What *does* happen is that ddd sees that it is in /usr/bin/m_test.py but it does *not* start a debugging session, since ddd fails to see that it is a python file(!), despite the fact that the very same file when specified locally is handled correctly.

example:
themusicgod1@Hedy:~/foob$ cd
themusicgod1@Hedy:~$ ddd m_test.py
(ddd window opens up with
GNU DDD 3.3.12 (x86_64-pc-linux-gnu), by Dorothea L"/usr/bin/m_test.py": not in executable format: File format not recognized
and with *gdb* rather than pydb running as the debugger in the session frame

ddd: 1:3.3.12-5.1build1
pydb: 1.26-2

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: ddd 1:3.3.12-5.1build1
ProcVersionSignature: Ubuntu 4.8.0-22.24-generic 4.8.0
Uname: Linux 4.8.0-22-generic x86_64
ApportVersion: 2.20.3-0ubuntu8
Architecture: amd64
CurrentDesktop: GNOME
Date: Tue Oct 18 19:45:02 2016
EcryptfsInUse: Yes
InstallationDate: Installed on 2014-07-09 (832 days ago)
InstallationMedia: Ubuntu-GNOME 14.10 "Utopic Unicorn" - Alpha amd64 (20140708)
SourcePackage: ddd
UpgradeStatus: Upgraded to yakkety on 2016-10-16 (2 days ago)