fix Arc.center being nan cause of switch to np.sqrt raising different error than math.sqrt

svgpathtools/path.py

@@ -1462,10 +1462,8 @@ class Arc(object):
         # plugging our transformed endpoints (x_1', y_1') and (x_2', y_2')
         tmp = rx_sqd*y1p_sqd + ry_sqd*x1p_sqd
         radicand = (rx_sqd*ry_sqd - tmp) / tmp
-        try:
-            radical = sqrt(radicand)
-        except ValueError:
-            radical = 0
+        radical = 0 if np.isclose(radicand, 0) else sqrt(radicand)
+
         if self.large_arc == self.sweep:
             cp = -radical*(rx*y1p/ry - 1j*ry*x1p/rx)
         else:

test/test_path.py

@@ -656,7 +656,9 @@ class ArcTest(unittest.TestCase):
                 orig_t = random.random()
                 p = a.point(orig_t)
                 computed_t = a.point_to_t(p)
-                self.assertAlmostEqual(orig_t, computed_t, msg="arc %s at t=%f is point %s, but got %f back" % (a, orig_t, p, computed_t))
+                self.assertAlmostEqual(orig_t, computed_t, 
+                    msg="arc %s at t=%f is point %s, but got %f back"
+                        "" % (a, orig_t, p, computed_t))
 
     def test_approx_quad(self):
         n = 100