Issue #15767: Introduce ModuleNotFoundError, a subclass of
ImportError.
The exception is raised by import when a module could not be found.
Technically this is defined as no viable loader could be found for the
specified module. This includes ``from ... import`` statements so that
the module usage is consistent for all situations where import
couldn't find what was requested.
This should allow for the common idiom of::
try:
import something
except ImportError:
pass
to be updated to using ModuleNotFoundError and not accidentally mask
ImportError messages that should propagate (e.g. issues with a
loader).
This work was driven by the fact that the ``from ... import``
statement needed to be able to tell the difference between an
ImportError that simply couldn't find a module (and thus silence the
exception so that ceval can raise it) and an ImportError that
represented an actual problem.
diff --git a/Python/ceval.c b/Python/ceval.c
index e184ef6..1e2637c 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -4588,7 +4588,7 @@
x = PyObject_GetAttr(v, name);
if (x == NULL && PyErr_ExceptionMatches(PyExc_AttributeError)) {
- PyErr_Format(PyExc_ImportError, "cannot import name %S", name);
+ PyErr_Format(PyExc_ModuleNotFoundError, "cannot import name %S", name);
}
return x;
}