Fix repr for negative imaginary part. Fixes #1013908.

Lib/test/test_complex.py

@@ -286,6 +286,7 @@ class ComplexTest(unittest.TestCase):
 
     def test_repr(self):
         self.assertEqual(repr(1+6j), '(1+6j)')
+        self.assertEqual(repr(1-6j), '(1-6j)')
 
     def test_neg(self):
         self.assertEqual(-(1+6j), -1-6j)

Objects/complexobject.c

@@ -279,11 +279,15 @@ complex_to_buf(char *buf, int bufsz, PyComplexObject *v, int precision)
 		strncat(buf, "j", bufsz);
 	} else {
 		char re[64], im[64];
-		
+		char *fmt;
 		PyOS_snprintf(format, 32, "%%.%ig", precision);
 		PyOS_ascii_formatd(re, 64, format, v->cval.real);
 		PyOS_ascii_formatd(im, 64, format, v->cval.imag);
-		PyOS_snprintf(buf, bufsz, "(%s+%sj)", re, im);
+		if (v->cval.imag < 0.)
+			fmt = "(%s%sj)";
+		else
+			fmt = "(%s+%sj)";
+		PyOS_snprintf(buf, bufsz, fmt, re, im);
 	}
 }