python: Use detect.find_external_dependency() for log consistency

py.find_installation().dependency() was not logging whether it is found
or not. Use find_external_dependency() for consistency.

mesonbuild/dependencies/detect.py

@@ -80,7 +80,7 @@ display_name_map = {
     'wxwidgets': 'WxWidgets',
 }
 
-def find_external_dependency(name: str, env: 'Environment', kwargs: T.Dict[str, object]) -> T.Union['ExternalDependency', NotFoundDependency]:
+def find_external_dependency(name: str, env: 'Environment', kwargs: T.Dict[str, object], candidates: T.Optional[T.List['DependencyGenerator']] = None) -> T.Union['ExternalDependency', NotFoundDependency]:
     assert name
     required = kwargs.get('required', True)
     if not isinstance(required, bool):
@@ -101,7 +101,8 @@ def find_external_dependency(name: str, env: 'Environment', kwargs: T.Dict[str,
     type_text = PerMachine('Build-time', 'Run-time')[for_machine] + ' dependency'
 
     # build a list of dependency methods to try
-    candidates = _build_external_dependency_list(name, env, for_machine, kwargs)
+    if candidates is None:
+        candidates = _build_external_dependency_list(name, env, for_machine, kwargs)
 
     pkg_exc: T.List[DependencyException] = []
     pkgdep:  T.List[ExternalDependency] = []

mesonbuild/modules/python.py

@@ -22,7 +22,7 @@ from .. import mlog
 from ..coredata import UserFeatureOption
 from ..build import known_shmod_kwargs
 from ..dependencies import NotFoundDependency
-from ..dependencies.detect import get_dep_identifier
+from ..dependencies.detect import get_dep_identifier, find_external_dependency
 from ..dependencies.python import BasicPythonExternalProgram, python_factory, _PythonDependencyBase
 from ..interpreter import ExternalProgramHolder, extract_required_kwarg, permitted_dependency_kwargs
 from ..interpreter import primitives as P_OBJ
@@ -185,12 +185,8 @@ class PythonInstallation(ExternalProgramHolder):
 
         new_kwargs = kwargs.copy()
         new_kwargs['required'] = False
-        # it's theoretically (though not practically) possible to not bind dep, let's ensure it is.
-        dep: Dependency = NotFoundDependency('python', self.interpreter.environment)
-        for d in python_factory(self.interpreter.environment, for_machine, new_kwargs, self.held_object):
-            dep = d()
-            if dep.found():
-                break
+        candidates = python_factory(self.interpreter.environment, for_machine, new_kwargs, self.held_object)
+        dep = find_external_dependency('python', self.interpreter.environment, new_kwargs, candidates)
 
         self.interpreter.coredata.deps[for_machine].put(identifier, dep)
         return dep