What causes "{type(self.cause).__name__}: {self.cause} (from {self.path})" in pytest-dev/pytest?

Read the wrapped cause in the message - the original exception type and text are preserved verbatim

pytest-dev/pytest · error · ConftestImportFailure

{type(self.cause).name}: {self.cause} (from {self.path})

Error message

{type(self.cause).__name__}: {self.cause} (from {self.path})

What it means

Raised by _try_load_conftest() at config/__init__.py:773 when import_path() fails while loading a conftest.py. Any exception during import is wrapped in ConftestImportFailure (defined at config/__init__.py:130) which preserves path and cause; __str__ at config/__init__.py:140-141 renders it as '<CauseType>: <cause msg> (from <path>)'. pytest surfaces this in its internal-error report and filters the traceback via filter_traceback_for_conftest_import_failure() (config/__init__.py:144).

Source

Thrown at src/_pytest/config/__init__.py:773

        # before loading the new one, otherwise the existing one will be
        # returned from the module cache.
        pkgpath = resolve_package_path(conftestpath)
        if pkgpath is None:
            try:
                del sys.modules[conftestpath.stem]
            except KeyError:
                pass

        try:
            mod = import_path(
                conftestpath,
                mode=importmode,
                root=rootpath,
                consider_namespace_packages=consider_namespace_packages,
            )
        except Exception as e:
            assert e.__traceback__ is not None
            raise ConftestImportFailure(conftestpath, cause=e) from e

        self._check_non_top_pytest_plugins(mod, conftestpath)

        self._conftest_plugins.add(mod)
        dirpath = conftestpath.parent
        if dirpath in self._dirpath2confmods:
            for path, mods in self._dirpath2confmods.items():
                if dirpath in path.parents or path == dirpath:
                    if mod in mods:
                        raise AssertionError(
                            f"While trying to load conftest path {conftestpath!s}, "
                            f"found that the module {mod} is already loaded with path {mod.__file__}. "
                            "This is not supposed to happen. Please report this issue to pytest."
                        )
                    mods.append(mod)
        self.trace(f"loading conftestmodule {mod!r}")
        self.consider_conftest(mod, registration_name=conftestpath_plugin_name)
        return mod

View on GitHub (pinned to 0d6fbdeffa)

Solutions

Read the wrapped cause in the message - the original exception type and text are preserved verbatim
Open the conftest.py at the reported path and fix the import/syntax error
Run `python -c "import <module>"` against the offending conftest to reproduce the error outside pytest
Check that any conftest-level plugin listed in pytest_plugins is pip-installed in the active environment

Example fix

// before
# conftest.py
import missing_dep  # ImportError
// after
# conftest.py
try:
    import missing_dep
except ImportError:
    missing_dep = None

Defensive patterns

Strategy: try-catch

Validate before calling

import ast
src = open('conftest.py').read()
ast.parse(src)  # catches syntax errors before pytest runs

Type guard

def conftest_imports_cleanly(path: str) -> bool:
    import importlib.util
    spec = importlib.util.spec_from_file_location('cf', path)
    mod = importlib.util.module_from_spec(spec)
    try:
        spec.loader.exec_module(mod)
        return True
    except Exception:
        return False

Try / catch

from _pytest.config import ConftestImportFailure
try:
    pytest.main(['tests'])
except ConftestImportFailure as e:
    print(f'{e.path}: {type(e.cause).__name__}: {e.cause}')

Prevention

Pre-validate conftest.py by importing it in isolation: python -c 'import conftest'
Keep conftest.py imports minimal and dependency-light
Use separate venv checks in CI to ensure all conftest dependencies are installed

When it happens

Trigger: A conftest.py at any level (rootdir, tests/, subdir) contains a SyntaxError, ImportError (missing dependency), NameError, or any exception at module top-level. capture.py:764-770 calls import_path(); the bare `except Exception as e` at capture.py:771 wraps it.

Common situations: Adding a new conftest.py that imports a not-yet-installed dependency; upgrading pytest plugins that change APIs; circular imports between conftest.py files; python path issues when rootdir is mis-detected.

Related errors

AI-assisted analysis of pytest-dev/pytest@0d6fbdeffa (2026-08-11). Data as JSON: /api/errors/474deb57a28bffa5. Report an issue: GitHub.