…n functions (GH-3)

Cython will, in the right circumstances, offer a MethodType instance
where im_func is a builtin function. Any instance of MethodType is
automatically assumed to be a Python-defined function (more
specifically, a function that has an inspectable signature), but
_set_signature was still conservative in its assumptions. As a result
_set_signature would return early with None instead of a mock since
the im_func had no inspectable signature. This causes problems
deeper inside mock, as _set_signature is assumed to _always_
return a mock, and nothing checked its return value.

In similar corner cases, autospec will simply not check the spec of the
function, so _set_signature is amended to now return early with the
original, not-wrapped mock object.

Patch by Aaron Gallagher.

…builtin functions (GH-3)

Cython will, in the right circumstances, offer a MethodType instance
where im_func is a builtin function. Any instance of MethodType is
automatically assumed to be a Python-defined function (more
specifically, a function that has an inspectable signature), but
_set_signature was still conservative in its assumptions. As a result
_set_signature would return early with None instead of a mock since
the im_func had no inspectable signature. This causes problems
deeper inside mock, as _set_signature is assumed to _always_
return a mock, and nothing checked its return value.

In similar corner cases, autospec will simply not check the spec of the
function, so _set_signature is amended to now return early with the
original, not-wrapped mock object.

Patch by Aaron Gallagher.

(cherry picked from commit 856cbcc)

…builtin functions (GH-3)

Cython will, in the right circumstances, offer a MethodType instance
where im_func is a builtin function. Any instance of MethodType is
automatically assumed to be a Python-defined function (more
specifically, a function that has an inspectable signature), but
_set_signature was still conservative in its assumptions. As a result
_set_signature would return early with None instead of a mock since
the im_func had no inspectable signature. This causes problems
deeper inside mock, as _set_signature is assumed to _always_
return a mock, and nothing checked its return value.

In similar corner cases, autospec will simply not check the spec of the
function, so _set_signature is amended to now return early with the
original, not-wrapped mock object.

Patch by Aaron Gallagher.

(cherry picked from commit 856cbcc)

…python#91466)

Fix an uninitialized bool in exception print context.
    
`struct exception_print_context.need_close` was uninitialized.
    
Found by oss-fuzz in a test case running under the undefined behavior sanitizer.
    
https://oss-fuzz.com/testcase-detail/6217746058182656
    
```
Python/pythonrun.c:1241:28: runtime error: load of value 253, which is not a valid value for type 'bool'
    #0 0xbf2203 in print_chained cpython3/Python/pythonrun.c:1241:28
    #1 0xbea4bb in print_exception_cause_and_context cpython3/Python/pythonrun.c:1320:19
    #2 0xbea4bb in print_exception_recursive cpython3/Python/pythonrun.c:1470:13
    #3 0xbe9e39 in _PyErr_Display cpython3/Python/pythonrun.c:1517:9
```
    
Pretty obvious what the ommission was upon code inspection.