add import-untyped-stubs-available, and docu (but not implementation)

Author: wyattscarpenter

docs/source/error_code_list.rst

@@ -640,7 +640,8 @@ Check for an issue with imports [import]
 ----------------------------------------
 
 Mypy generates an error if it can't resolve an `import` statement.
-This is a parent error code of `import-not-found` and `import-untyped`
+This is a parent error code of `import-not-found`, `import-untyped`,
+and `import-untyped-stubs-available`
 
 See :ref:`ignore-missing-imports` for how to work around these errors.
 
@@ -673,14 +674,33 @@ Example:
 
 .. code-block:: python
 
-    # Error: Library stubs not installed for "bs4"  [import-untyped]
+    # Error: Library stubs not installed for "bs4"  [import-untyped-stubs-available]
     import bs4
     # Error: Skipping analyzing "no_py_typed": module is installed, but missing library stubs or py.typed marker  [import-untyped]
     import no_py_typed
 
 In some cases, these errors can be fixed by installing an appropriate
 stub package. See :ref:`ignore-missing-imports` for more details.
 
+Check that import target with known stubs can be found [import-untyped-stubs-available]
+--------------------------------------------------------
+
+Like :ref:`code-import-untyped`, but used when mypy knows there is an appropriate
+type stub package corresponding to the library, which you could install.
+
+Example:
+
+.. code-block:: python
+
+    # Error: Library stubs not installed for "bs4"  [import-untyped-stubs-available]
+    import bs4
+    # Error: Skipping analyzing "no_py_typed": module is installed, but missing library stubs or py.typed marker  [import-untyped]
+    import no_py_typed
+
+These errors can be fixed by installing the appropriate
+stub package. See :ref:`ignore-missing-imports` for more details.
+
+
 .. _code-no-redef:
 
 Check that each name is defined once [no-redef]

mypy/errorcodes.py

@@ -113,6 +113,9 @@ def __hash__(self) -> int:
 IMPORT_UNTYPED: Final = ErrorCode(
     "import-untyped", "Require that imported module has stubs", "General", sub_code_of=IMPORT
 )
+IMPORT_UNTYPED_STUBS_AVAILABLE: Final = ErrorCode(
+    "import-untyped-stubs-available", "Require that imported module (with known stubs) has stubs", "General", sub_code_of=IMPORT
+)
 NO_REDEF: Final = ErrorCode("no-redef", "Check that each name is defined once", "General")
 FUNC_RETURNS_VALUE: Final = ErrorCode(
     "func-returns-value", "Check that called function returns a value in value context", "General"