pytest.approx: import numpy conditionally (#13563)

This matches existing conditional-import behavior in `pytest.approx`, and improves runtime for users of `pytest.approx` and not `numpy`.

Author: tybug

AUTHORS

@@ -261,6 +261,7 @@ Leonardus Chen
 Lev Maximov
 Levon Saldamli
 Lewis Cowles
+Liam DeVoe
 Llandy Riveron Del Risco
 Loic Esteve
 lovetheguitar

changelog/13563.bugfix.rst

@@ -0,0 +1 @@
+:func:`pytest.approx` now only imports ``numpy`` if NumPy is already in ``sys.modules``. This fixes unconditional import behavior introduced in `8.4.0`.

src/_pytest/python_api.py

@@ -426,12 +426,9 @@ def is_bool(val: Any) -> bool:
             # Check if `val` is a native bool or numpy bool.
             if isinstance(val, bool):
                 return True
-            try:
-                import numpy as np
-
+            if np := sys.modules.get("numpy"):
                 return isinstance(val, np.bool_)
-            except ImportError:
-                return False
+            return False
 
         asarray = _as_numpy_array(actual)
         if asarray is not None: