Avoid ambiguous error return value in tests.

tests/run/nogil.pyx

@@ -28,10 +28,10 @@ cdef int g(int x) nogil:
         y = x + 42
         return y
 
-cdef int with_gil_func() except 0 with gil:
+cdef int with_gil_func() except -1 with gil:
     raise Exception("error!")
 
-cdef int nogil_func() nogil except 0:
+cdef int nogil_func() nogil except -1:
     with_gil_func()
 
 def test_nogil_exception_propagation():

tests/run/sequential_parallel.pyx

@@ -660,7 +660,7 @@ def outer_parallel_section():
         sum += inner_parallel_section()
     return sum
 
-cdef int nogil_cdef_except_clause() nogil except 0:
+cdef int nogil_cdef_except_clause() nogil except -1:
     return 1
 
 cdef void nogil_cdef_except_star() nogil except *: