fix _Py_c_quot() instead

Author: skirpichev

Objects/complexobject.c

@@ -105,7 +105,7 @@ _Py_c_quot(Py_complex a, Py_complex b)
             const double ratio = b.imag / b.real;
             const double denom = b.real + b.imag * ratio;
             r.real = (a.real + a.imag * ratio) / denom;
-            r.imag = (a.imag - a.real * ratio) / denom;
+            r.imag = (a.imag ? a.imag - a.real * ratio : -a.real * ratio) / denom;
         }
     }
     else if (abs_bimag >= abs_breal) {
@@ -177,12 +177,10 @@ c_powu(Py_complex x, long n)
 static Py_complex
 c_powi(Py_complex x, long n)
 {
-    if (n > 0)
-        return c_powu(x,n);
-    else {
-        c_1.imag = -copysign(0.0, x.imag);
+    if (n < 0)
         return _Py_c_quot(c_1, c_powu(x,-n));
-    }
+    else
+        return c_powu(x,n);
 }
 
 double