Checkbox snappy - import python failing in Merge #336741

earlier with below git id

Merge #330604 from ~kissiel/checkbox-snappy:hw-submission

adding python plugin in snapcraft.yaml - able to built the checkbox snap

@@ -54,6 +58,11 @@ parts:
     after: [plainbox-provider-tpm2]
   plainbox-provider-engineering-tests:
     after: [plainbox-provider-sru]
+  python-import:
+    plugin: python
+    python-packages:
+           - pyserial
+

but with the latest release of checkbox-snappy code
Merge #336741 from ~sylvain-pineau/checkbox-snappy:no_plainbox

adding the same python-import is failing

plainbox-provider-engineering-tests' has prerequisites that need to be staged: plainbox-provider-sru
Parts 'checkbox-support-dev' and 'python-import' have the following file paths in common which have different contents:
    usr/lib/python3.5/base64.py
    usr/lib/python3.5/cProfile.py
    usr/lib/python3.5/cgi.py
    usr/lib/python3.5/encodings/rot_13.py
    usr/lib/python3.5/idlelib/PyShell.py
    usr/lib/python3.5/keyword.py
    usr/lib/python3.5/lib2to3/pgen2/token.py
    usr/lib/python3.5/pdb.py
    usr/lib/python3.5/platform.py
    usr/lib/python3.5/profile.py
    usr/lib/python3.5/pydoc.py
    usr/lib/python3.5/quopri.py
    usr/lib/python3.5/sitecustomize.py
    usr/lib/python3.5/smtpd.py
    usr/lib/python3.5/smtplib.py
    usr/lib/python3.5/symbol.py
    usr/lib/python3.5/tabnanny.py
    usr/lib/python3.5/tarfile.py
    usr/lib/python3.5/test/pystone.py
    usr/lib/python3.5/test/regrtest.py
    usr/lib/python3.5/timeit.py
    usr/lib/python3.5/trace.py
    usr/lib/python3.5/uu.py
    usr/lib/python3.5/webbrowser.py
    usr/share/dh-python/dh_pypy
    usr/share/dh-python/dh_python2
    usr/share/dh-python/dh_python3
    usr/share/dh-python/dhpython/_defaults.py
    usr/share/dh-python/pybuild
    usr/share/python3/py3versions.py

Snapcraft offers some capabilities to solve this by use of the following keywords:
    - `filesets`
    - `stage`
    - `snap`
    - `organize`

Learn more about these part keywords by running `snapcraft help plugins`