Fix test for changes to NumPy

Before:

[[ 0.  0.  0. ]
 [ 0.  0.  0. ]
 [ 0.  0.  0. ]]

With recent NumPy:

[[0.  0.  0.]
 [0.  0.  0.]
 [0.  0.  0.]]

See numpy/numpy#9139

Author: bchretien

tests/to-python.cc

@@ -36,6 +36,7 @@ BOOST_AUTO_TEST_CASE (redir)
   ToPython tp;
 
   tp << "import numpy as np"
+     << "np.set_printoptions(formatter={'all': lambda x: str(x)})"
      << "ar = np.zeros((3,3))"
      << "print(ar)"
      << "ar[0,1] = 42."

tests/to-python.stdout

@@ -1,4 +1,4 @@
-[[ 0.  0.  0.]
- [ 0.  0.  0.]
- [ 0.  0.  0.]]
+[[0.0 0.0 0.0]
+ [0.0 0.0 0.0]
+ [0.0 0.0 0.0]]
 42.0