TST: skip test_dviread if kpsewhich is not available

Also fix the docstring to mention that it is part of miktex...

lib/matplotlib/dviread.py

@@ -961,8 +961,8 @@ def find_tex_file(filename, format=None):
     `--format` option.
 
     Apparently most existing TeX distributions on Unix-like systems
-    use kpathsea. I hear MikTeX (a popular distribution on Windows)
-    doesn't use kpathsea, so what do we do? (TODO)
+    use kpathsea. It's also available as part of MikTeX, a popular
+    distribution on Windows.
 
     .. seealso::
 

lib/matplotlib/tests/test_dviread.py

@@ -2,6 +2,8 @@
                         unicode_literals)
 
 from matplotlib.externals import six
+from matplotlib.compat.subprocess import check_output
+
 
 from nose.tools import assert_equal, with_setup
 import matplotlib.dviread as dr
@@ -61,6 +63,11 @@ def test_PsfontsMap():
 
 
 def test_dviread():
+    try:
+        check_output(["kpsewhich", "-version"])
+    except:
+        raise SkipTest('kpsewhich is required')
+
     dir = os.path.join(os.path.dirname(__file__), 'baseline_images', 'dviread')
     with open(os.path.join(dir, 'test.json')) as f:
         correct = json.load(f)