Fix C API docs: PyCapsule_Import always set an exception on failure. (GH-6967)

(cherry picked from commit bde3e0bf)
Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>

Doc/c-api/capsule.rst

@@ -9,6 +9,8 @@ Capsules
 
 Refer to :ref:`using-capsules` for more information on using these objects.
 
+.. versionadded:: 3.1
+
 
 .. c:type:: PyCapsule
 
@@ -19,6 +21,7 @@ Refer to :ref:`using-capsules` for more information on using these objects.
    regular import mechanism can be used to access C APIs defined in dynamically
    loaded modules.
 
+
 .. c:type:: PyCapsule_Destructor
 
    The type of a destructor callback for a capsule.  Defined as::
@@ -104,8 +107,8 @@ Refer to :ref:`using-capsules` for more information on using these objects.
    import the module conventionally (using :c:func:`PyImport_ImportModule`).
 
    Return the capsule's internal *pointer* on success.  On failure, set an
-   exception and return *NULL*.  However, if :c:func:`PyCapsule_Import` failed to
-   import the module, and *no_block* was true, no exception is set.
+   exception and return *NULL*.
+
 
 .. c:function:: int PyCapsule_IsValid(PyObject *capsule, const char *name)
 
@@ -122,18 +125,21 @@ Refer to :ref:`using-capsules` for more information on using these objects.
    Return a nonzero value if the object is valid and matches the name passed in.
    Return ``0`` otherwise.  This function will not fail.
 
+
 .. c:function:: int PyCapsule_SetContext(PyObject *capsule, void *context)
 
    Set the context pointer inside *capsule* to *context*.
 
    Return ``0`` on success.  Return nonzero and set an exception on failure.
 
+
 .. c:function:: int PyCapsule_SetDestructor(PyObject *capsule, PyCapsule_Destructor destructor)
 
    Set the destructor inside *capsule* to *destructor*.
 
    Return ``0`` on success.  Return nonzero and set an exception on failure.
 
+
 .. c:function:: int PyCapsule_SetName(PyObject *capsule, const char *name)
 
    Set the name inside *capsule* to *name*.  If non-*NULL*, the name must
@@ -142,6 +148,7 @@ Refer to :ref:`using-capsules` for more information on using these objects.
 
    Return ``0`` on success.  Return nonzero and set an exception on failure.
 
+
 .. c:function:: int PyCapsule_SetPointer(PyObject *capsule, void *pointer)
 
    Set the void pointer inside *capsule* to *pointer*.  The pointer may not be