Issue #15767: Add ModuleNotFoundError.
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 336c32c..6fb5eb7 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -706,6 +706,13 @@
                         "module.");
 
 /*
+ *    ModuleNotFoundError extends ImportError
+ */
+
+MiddlingExtendsException(PyExc_ImportError, ModuleNotFoundError, ImportError,
+                         "Module not found.");
+
+/*
  *    OSError extends Exception
  */
 
@@ -2469,6 +2476,7 @@
     PRE_INIT(SystemExit)
     PRE_INIT(KeyboardInterrupt)
     PRE_INIT(ImportError)
+    PRE_INIT(ModuleNotFoundError)
     PRE_INIT(OSError)
     PRE_INIT(EOFError)
     PRE_INIT(RuntimeError)
@@ -2541,6 +2549,7 @@
     POST_INIT(SystemExit)
     POST_INIT(KeyboardInterrupt)
     POST_INIT(ImportError)
+    POST_INIT(ModuleNotFoundError)
     POST_INIT(OSError)
     INIT_ALIAS(EnvironmentError, OSError)
     INIT_ALIAS(IOError, OSError)