Improve load_torchcodec_shared_libraries error reporting

[JAEarly]

Added when investigated issues related to #1023.
Doesn't fix the underlying issue, but improves error reporting for users.

[NicolasHug]

Thanks for the PR @JAEarly

Can you share what the old and new tracebacks look like?

[JAEarly]

This should help with issues such as #1006

[JAEarly]

Old:

>       raise RuntimeError(
            f"""Could not load libtorchcodec. Likely causes:
              1. FFmpeg is not properly installed in your environment. We support
                 versions 4, 5, 6, and 7 on all platforms, and 8 on Mac and Linux.
              2. The PyTorch version ({torch.__version__}) is not compatible with
                 this version of TorchCodec. Refer to the version compatibility
                 table:
                 https://github.com/pytorch/torchcodec?tab=readme-ov-file#installing-torchcodec.
              3. Another runtime dependency; see exceptions below.
            The following exceptions were raised as we tried to load libtorchcodec:
            """
            f"{traceback}"
        )
E       RuntimeError: Could not load libtorchcodec. Likely causes:
E                 1. FFmpeg is not properly installed in your environment. We support
E                    versions 4, 5, 6, and 7 on all platforms, and 8 on Mac and Linux.
E                 2. The PyTorch version (2.9.1) is not compatible with
E                    this version of TorchCodec. Refer to the version compatibility
E                    table:
E                    https://github.com/pytorch/torchcodec?tab=readme-ov-file#installing-torchcodec.
E                 3. Another runtime dependency; see exceptions below.
E               The following exceptions were raised as we tried to load libtorchcodec:
E
E       [start of libtorchcodec loading traceback]
E       FFmpeg version 8: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core8.dylib
E       FFmpeg version 7: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core7.dylib
E       FFmpeg version 6: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core6.dylib
E       FFmpeg version 5: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core5.dylib
E       FFmpeg version 4: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core4.dylib
E       [end of libtorchcodec loading traceback].

.venv/lib/python3.10/site-packages/torchcodec/_core/ops.py:69: RuntimeError

New:

>       raise RuntimeError(
            f"""Could not load libtorchcodec. Likely causes:
              1. FFmpeg is not properly installed in your environment. We support
                 versions 4, 5, 6, and 7 on all platforms, and 8 on Mac and Linux.
              2. The PyTorch version ({torch.__version__}) is not compatible with
                 this version of TorchCodec. Refer to the version compatibility
                 table:
                 https://github.com/pytorch/torchcodec?tab=readme-ov-file#installing-torchcodec.
              3. Another runtime dependency; see exceptions below.
            The following exceptions were raised as we tried to load libtorchcodec:
            """
            f"{full_traceback}"
        )
E       RuntimeError: Could not load libtorchcodec. Likely causes:
E                 1. FFmpeg is not properly installed in your environment. We support
E                    versions 4, 5, 6, and 7 on all platforms, and 8 on Mac and Linux.
E                 2. The PyTorch version (2.9.1) is not compatible with
E                    this version of TorchCodec. Refer to the version compatibility
E                    table:
E                    https://github.com/pytorch/torchcodec?tab=readme-ov-file#installing-torchcodec.
E                 3. Another runtime dependency; see exceptions below.
E               The following exceptions were raised as we tried to load libtorchcodec:
E
E       [start of libtorchcodec loading traceback]
E       FFmpeg version 8: Traceback (most recent call last):
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torch/_ops.py", line 1488, in load_library
E           ctypes.CDLL(path)
E         File "/nix/store/ra1l4hyhxw3zlq62y8vg6fpxysq9ln6s-python3-3.10.16/lib/python3.10/ctypes/__init__.py", line 374, in __init__
E           self._handle = _dlopen(self._name, mode)
E       OSError: dlopen(/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core8.dylib, 0x0006): Library not loaded: @rpath/libavutil.60.dylib
E         Referenced from: <5D38709A-E4F4-3C1B-A53D-CBBDCAC56C91> /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core8.dylib
E         Reason: no LC_RPATH's found
E
E       The above exception was the direct cause of the following exception:
E
E       Traceback (most recent call last):
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/_core/ops.py", line 52, in load_torchcodec_shared_libraries
E           torch.ops.load_library(core_library_path)
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torch/_ops.py", line 1490, in load_library
E           raise OSError(f"Could not load this library: {path}") from e
E       OSError: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core8.dylib
E
E       FFmpeg version 7: Traceback (most recent call last):
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torch/_ops.py", line 1488, in load_library
E           ctypes.CDLL(path)
E         File "/nix/store/ra1l4hyhxw3zlq62y8vg6fpxysq9ln6s-python3-3.10.16/lib/python3.10/ctypes/__init__.py", line 374, in __init__
E           self._handle = _dlopen(self._name, mode)
E       OSError: dlopen(/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core7.dylib, 0x0006): Library not loaded: @rpath/libavutil.59.dylib
E         Referenced from: <D3303F7C-612B-31D2-BBE7-8824565D3187> /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core7.dylib
E         Reason: no LC_RPATH's found
E
E       The above exception was the direct cause of the following exception:
E
E       Traceback (most recent call last):
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/_core/ops.py", line 52, in load_torchcodec_shared_libraries
E           torch.ops.load_library(core_library_path)
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torch/_ops.py", line 1490, in load_library
E           raise OSError(f"Could not load this library: {path}") from e
E       OSError: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core7.dylib
E
E       FFmpeg version 6: Traceback (most recent call last):
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torch/_ops.py", line 1488, in load_library
E           ctypes.CDLL(path)
E         File "/nix/store/ra1l4hyhxw3zlq62y8vg6fpxysq9ln6s-python3-3.10.16/lib/python3.10/ctypes/__init__.py", line 374, in __init__
E           self._handle = _dlopen(self._name, mode)
E       OSError: dlopen(/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core6.dylib, 0x0006): Library not loaded: @rpath/libavutil.58.dylib
E         Referenced from: <AD6D6E09-CED2-3AB1-A98A-AAAE9D2F0689> /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core6.dylib
E         Reason: no LC_RPATH's found
E
E       The above exception was the direct cause of the following exception:
E
E       Traceback (most recent call last):
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/_core/ops.py", line 52, in load_torchcodec_shared_libraries
E           torch.ops.load_library(core_library_path)
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torch/_ops.py", line 1490, in load_library
E           raise OSError(f"Could not load this library: {path}") from e
E       OSError: Could not load this library: /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core6.dylib
E
E       FFmpeg version 5: Traceback (most recent call last):
E         File "/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torch/_ops.py", line 1488, in load_library
E           ctypes.CDLL(path)
E         File "/nix/store/ra1l4hyhxw3zlq62y8vg6fpxysq9ln6s-python3-3.10.16/lib/python3.10/ctypes/__init__.py", line 374, in __init__
E           self._handle = _dlopen(self._name, mode)
E       OSError: dlopen(/Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core5.dylib, 0x0006): Library not loaded: @rpath/libavutil.57.dylib
E         Referenced from: <AD04BD63-F8C4-3823-98F4-1D58CB19DB81> /Users/user/Projects/some_project/.venv/lib/python3.10/site-packages/torchcodec/libtorchcodec_core5.dylib
E         Reason: no LC_RPATH's found
E
E       The above exception was the direct cause of the following exception:
E