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/Objects/exceptions.c b/Objects/exceptions.c
index 79bbb8f..23f6605 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -710,6 +710,13 @@
"module.");
/*
+ * ModuleNotFoundError extends ImportError
+ */
+
+MiddlingExtendsException(PyExc_ImportError, ModuleNotFoundError, ImportError,
+ "Module not found.");
+
+/*
* OSError extends Exception
*/
@@ -2395,6 +2402,7 @@
PRE_INIT(SystemExit)
PRE_INIT(KeyboardInterrupt)
PRE_INIT(ImportError)
+ PRE_INIT(ModuleNotFoundError)
PRE_INIT(OSError)
PRE_INIT(EOFError)
PRE_INIT(RuntimeError)
@@ -2465,6 +2473,7 @@
POST_INIT(SystemExit)
POST_INIT(KeyboardInterrupt)
POST_INIT(ImportError)
+ POST_INIT(ModuleNotFoundError)
POST_INIT(OSError)
INIT_ALIAS(EnvironmentError, OSError)
INIT_ALIAS(IOError, OSError)