Pure real results for pure real complex powers.

Cython/Utility/Complex.c

@@ -264,6 +264,10 @@ static {{type}} __Pyx_PyComplex_As_{{type_name}}(PyObject* o) {
             if (a.imag == 0) {
                 if (a.real == 0) {
                     return a;
+                } else if (b.imag == 0) {
+                    z.real = pow{{m}}(a.real, b.real);
+                    z.imag = 0;
+                    return z;
                 } else if (a.real > 0) {
                     r = a.real;
                     theta = 0;

tests/run/complex_numbers_T305.pyx

@@ -64,6 +64,8 @@ def test_int_pow(double complex z, int n, tol=None):
     [True, True, True, True, True, True, True, True, True]
     >>> [test_int_pow(complex(2, 0.5), k, 1e-14) for k in range(0, 10)]
     [True, True, True, True, True, True, True, True, True, True]
+    >>> test_int_pow(-0.5, 5, tol=1e-15)
+    True
     """
     if tol is None:
         return z**n + <object>0 # add zero to normalize zero sign