The coverity scan was run on python2, however the same defect seems to exist in python3 as well.

Error: RESOURCE_LEAK (CWE-772): [#def69]
Python-2.7.15/Objects/longobject.c:3793: alloc_fn: Storage is returned from allocation function "_PyLong_New".
Python-2.7.15/Objects/longobject.c:76:5: alloc_fn: Storage is returned from allocation function "PyObject_Malloc".
Python-2.7.15/Objects/obmalloc.c:982:5: alloc_fn: Storage is returned from allocation function "malloc".
Python-2.7.15/Objects/obmalloc.c:982:5: return_alloc_fn: Directly returning storage allocated by "malloc".
Python-2.7.15/Objects/longobject.c:76:5: identity_transfer: Passing "(PyVarObject *)PyObject_Malloc((size_t)(PyLong_Type.tp_basicsize + size * PyLong_Type.tp_itemsize + 7L & 0xfffffffffffffff8L))" as argument 1 to function "PyObject_InitVar", which returns that argument.
Python-2.7.15/Objects/object.c:237:5: return_parm: Returning parameter "op".
Python-2.7.15/Objects/longobject.c:76:5: return_alloc_fn: Directly returning storage allocated by "PyObject_InitVar".
Python-2.7.15/Objects/longobject.c:3793: var_assign: Assigning: "z" = storage returned from "_PyLong_New(size_a)".
Python-2.7.15/Objects/longobject.c:3797: var_assign: Assigning: "a" = "z".
Python-2.7.15/Objects/longobject.c:3847: leaked_storage: Variable "z" going out of scope leaks the storage it points to.
Python-2.7.15/Objects/longobject.c:3847: leaked_storage: Returning without freeing "a" leaks the storage that it points to.
 3845|       default:
 3846|           PyErr_BadArgument();
 3847|->         return NULL;
 3848|       }
 3849|   

Error: RESOURCE_LEAK (CWE-772): [#def70]
Python-2.7.15/Objects/longobject.c:3793: alloc_fn: Storage is returned from allocation function "_PyLong_New".
Python-2.7.15/Objects/longobject.c:76:5: alloc_fn: Storage is returned from allocation function "PyObject_Malloc".
Python-2.7.15/Objects/obmalloc.c:982:5: alloc_fn: Storage is returned from allocation function "malloc".
Python-2.7.15/Objects/obmalloc.c:982:5: return_alloc_fn: Directly returning storage allocated by "malloc".
Python-2.7.15/Objects/longobject.c:76:5: identity_transfer: Passing "(PyVarObject *)PyObject_Malloc((size_t)(PyLong_Type.tp_basicsize + size * PyLong_Type.tp_itemsize + 7L & 0xfffffffffffffff8L))" as argument 1 to function "PyObject_InitVar", which returns that argument.
Python-2.7.15/Objects/object.c:237:5: return_parm: Returning parameter "op".
Python-2.7.15/Objects/longobject.c:76:5: return_alloc_fn: Directly returning storage allocated by "PyObject_InitVar".
Python-2.7.15/Objects/longobject.c:3793: var_assign: Assigning: "z" = storage returned from "_PyLong_New(size_a)".
Python-2.7.15/Objects/longobject.c:3797: var_assign: Assigning: "a" = "z".
Python-2.7.15/Objects/longobject.c:3820: var_assign: Assigning: "z" = "a".
Python-2.7.15/Objects/longobject.c:3820: var_assign: Assigning: "b" = "z".
Python-2.7.15/Objects/longobject.c:3847: leaked_storage: Variable "z" going out of scope leaks the storage it points to.
Python-2.7.15/Objects/longobject.c:3847: leaked_storage: Returning without freeing "b" leaks the storage that it points to.
 3845|       default:
 3846|           PyErr_BadArgument();
 3847|->         return NULL;
 3848|       }
 3849|

This code is unreachable. Will mark it as such.

New changeset a10d426bab66a4e1f20d5e1b9aee3dbb435cf309 by Victor Stinner (stratakis) in branch 'master':
bpo-36292:  Mark unreachable code as such in long bitwise ops (GH-12333)
https://github.com/python/cpython/commit/a10d426bab66a4e1f20d5e1b9aee3dbb435cf309

I hope that the change will satisfy the god of static analyzers :-)

I discussed with Charalampos and we agreed to not backport this change, since it's a false alarm and not a real bug. I close the issue.