TST: fix test errors for Pathlib usage tests in io.py.

Pathlib was only added to the stdlib in Python 3.4, and there it
can handle string type input for a file with UTF8 encoding.
But the Patlib version on PyPi that can be installed for Python 2.7
doesn't accept strings, gives errors like:

    ======================================================================
    ERROR: test_ndfromtxt (test_io.TestPathUsage)
    ----------------------------------------------------------------------
    Traceback (most recent call last):
      File "/home/rgommers/Code/numpy/numpy/testing/decorators.py", line 147, in skipper_func
        return f(*args, **kwargs)
      File "/home/rgommers/Code/numpy/numpy/lib/tests/test_io.py", line 1888, in test_ndfromtxt
        f.write('1 2\n3 4')
    TypeError: must be unicode, not str

1 files changed, 13 insertions, 10 deletions

diff --git a/numpy/lib/tests/test_io.py b/numpy/lib/tests/test_io.py
index 720f2e74e..3b0b83712 100644
--- a/numpy/lib/tests/test_io.py
+++ b/numpy/lib/tests/test_io.py
@@ -1869,7 +1869,7 @@ class TestPathUsage(TestCase):
             data = np.load(path)
             assert_array_equal(data['lab'], 'place holder')
             data.close()
-    
+
     @np.testing.dec.skipif(Path is None, "No pathlib.Path")
     def test_genfromtxt(self):
         with temppath(suffix='.txt') as path:
@@ -1878,49 +1878,52 @@ class TestPathUsage(TestCase):
             np.savetxt(path, a)
             data = np.genfromtxt(path)
             assert_array_equal(a, data)
-    
+
     @np.testing.dec.skipif(Path is None, "No pathlib.Path")
     def test_ndfromtxt(self):
         # Test outputing a standard ndarray
         with temppath(suffix='.txt') as path:
             path = Path(path)
             with path.open('w') as f:
-                f.write('1 2\n3 4')
+                f.write(u'1 2\n3 4')
+
             control = np.array([[1, 2], [3, 4]], dtype=int)
             test = np.ndfromtxt(path, dtype=int)
             assert_array_equal(test, control)
-    
+
     @np.testing.dec.skipif(Path is None, "No pathlib.Path")
     def test_mafromtxt(self):
         # From `test_fancy_dtype_alt` above
         with temppath(suffix='.txt') as path:
             path = Path(path)
             with path.open('w') as f:
-                f.write('1,2,3.0\n4,5,6.0\n')
-                
+                f.write(u'1,2,3.0\n4,5,6.0\n')
+
             test = np.mafromtxt(path, delimiter=',')
             control = ma.array([(1.0, 2.0, 3.0), (4.0, 5.0, 6.0)])
             assert_equal(test, control)
-    
+
     @np.testing.dec.skipif(Path is None, "No pathlib.Path")
     def test_recfromtxt(self):
         with temppath(suffix='.txt') as path:
             path = Path(path)
             with path.open('w') as f:
-                f.write('A,B\n0,1\n2,3')
+                f.write(u'A,B\n0,1\n2,3')
+
             kwargs = dict(delimiter=",", missing_values="N/A", names=True)
             test = np.recfromtxt(path, **kwargs)
             control = np.array([(0, 1), (2, 3)],
                                dtype=[('A', np.int), ('B', np.int)])
             self.assertTrue(isinstance(test, np.recarray))
             assert_equal(test, control)
-    
+
     @np.testing.dec.skipif(Path is None, "No pathlib.Path")
     def test_recfromcsv(self):
         with temppath(suffix='.txt') as path:
             path = Path(path)
             with path.open('w') as f:
-                f.write('A,B\n0,1\n2,3')
+                f.write(u'A,B\n0,1\n2,3')
+
             kwargs = dict(missing_values="N/A", names=True, case_sensitive=True)
             test = np.recfromcsv(path, dtype=None, **kwargs)
             control = np.array([(0, 1), (2, 3)],