test: use ModuleNotFoundError in interface_ipc.py #34409

1. 
   fanquake commented at 11:58 am on January 26, 2026: member

   Change this so we catch the case where the capnp shared libs have been updated, and can no-longer be loaded by the Python module, resulting in a skipped test, even though pycapnp is installed. i.e:

    0stderr:
    1Traceback (most recent call last):
    2  File "/root/ci_scratch/build/test/functional/interface_ipc.py", line 20, in <module>
    3    import capnp  # type: ignore[import] # noqa: F401
    4    ^^^^^^^^^^^^
    5  File "/usr/local/lib64/python3.14/site-packages/capnp/__init__.py", line 36, in <module>
    6    from .version import version as __version__
    7  File "/usr/local/lib64/python3.14/site-packages/capnp/version.py", line 1, in <module>
    8    from .lib.capnp import _CAPNP_VERSION_MAJOR as LIBCAPNP_VERSION_MAJOR  # noqa: F401
    9    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   10ImportError: libcapnpc.so.1.0.1: cannot open shared object file: No such file or directory
   

   Failing in this way should make it clear that pycapnp needs to be reinstalled/rebuilt.

   If pycapnp is not installed, the test still skips as expected:

   0Remaining jobs: [interface_ipc.py]
   11/1 - interface_ipc.py skipped (capnp module not available.)
   2
   3TEST             | STATUS    | DURATION
   4
   5interface_ipc.py | ○ Skipped | 0 s
   

   Fixes: #34016.

2. test: use ModuleNotFoundError in interface_ipc.py

   Change this so we catch the case where the capnp shared libs have been
   updated, and can no-longer be loaded by the Python module, resulting in
   a skipped test, even though pycapnp is installed. i.e:
   ```bash
   stderr:
   Traceback (most recent call last):
     File "/root/ci_scratch/build/test/functional/interface_ipc.py", line 20, in <module>
       import capnp  # type: ignore[import] # noqa: F401
       ^^^^^^^^^^^^
     File "/usr/local/lib64/python3.14/site-packages/capnp/__init__.py", line 36, in <module>
       from .version import version as __version__
     File "/usr/local/lib64/python3.14/site-packages/capnp/version.py", line 1, in <module>
       from .lib.capnp import _CAPNP_VERSION_MAJOR as LIBCAPNP_VERSION_MAJOR  # noqa: F401
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   ImportError: libcapnpc.so.1.0.1: cannot open shared object file: No such file or directory
   ```
   
   Failing in this way should make it clear that `pycapnp` needs to be
   reinstalled/rebuilt.
   
   If  `pycapnp` is not installed, the test still skips as expected:
   ```bash
   Remaining jobs: [interface_ipc.py]
   1/1 - interface_ipc.py skipped (capnp module not available.)
   
   TEST             | STATUS    | DURATION
   
   interface_ipc.py | ○ Skipped | 0 s
   ```
   
   Fixes: #34016.
   
   Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

   905dfdee86
3. DrahtBot added the label Tests on Jan 26, 2026
4. 
   DrahtBot commented at 11:58 am on January 26, 2026: contributor

   The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

   Code Coverage & Benchmarks

   For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/34409.

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5. 
   maflcko commented at 1:04 pm on January 26, 2026: member

   lgtm ACK 905dfdee86d679f8ea31d841bceb77a5724a6b1b

   I have not tested this.

6. hebasto approved
7. 
   hebasto commented at 1:14 pm on January 26, 2026: member

   ACK 905dfdee86d679f8ea31d841bceb77a5724a6b1b, I have reviewed the code and it looks OK. However, I’m not able to reproduce #34016.

Contributors
fanquake DrahtBot maflcko hebasto

Labels
Tests