fix: fail fast if testinfra plugin is detected

To avoid confusing error messages, fail fast if testinfra plugin
is detected.

- #509
- pytest-dev/pytest-testinfra#58

Author: ssbarnea

.config/dictionary.txt

@@ -50,6 +50,7 @@ pytrace
 reportinfo
 runpytest
 superfences
+testinfra
 testpaths
 webservers
 xunit

src/pytest_ansible/plugin.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import importlib.util
 import logging
 import shutil
 import subprocess  # noqa: S404
@@ -103,9 +104,16 @@ def pytest_addoption(parser: pytest.Parser) -> None:
 
     Args:
         parser: pytest.Parser
+
+    Raises:
+        pytest.UsageError: If pytest-testinfra is installed.
     """
     if not HAS_ANSIBLE:
         return
+    spec = importlib.util.find_spec("testinfra")
+    if spec is not None:
+        msg = "pytest-ansible is incompatible with pytest-testinfra, see https://github.com/ansible/pytest-ansible/issues/509"
+        raise pytest.UsageError(msg)
     group = parser.getgroup("pytest-ansible")
     group.addoption(
         "--inventory",