test PR build with latest mxnet master

[roywei]

Summary

• Note this change is directly going to master branch since it's a change on CI
• Changing PR builds to use the latest mxnet master (pip install mxnet-mkl --pre) so development is not blocked by mxnet release. We can test with mxnet latest features in PR build on dev branch
• Nightly build still remains to test with mxnet stable release

[kalyc]

Seeing this error in PR -

[gw1] [ 98%] FAILED tests/keras/utils/vis_utils_test.py::test_plot_model [gw0] [100%] PASSED tests/keras/utils/data_utils_test.py::test_finite_generator_enqueuer_threads

=================================== FAILURES =================================== ___ test_plot_model ____ [gw1] linux -- Python 3.6.5 /usr/local/bin/python3.6

def test_plot_model():
    model = Sequential()
    model.add(Conv2D(2, kernel_size=(2, 3), input_shape=(3, 5, 5), name='conv'))
    model.add(Flatten(name='flat'))
    model.add(Dense(5, name='dense1'))

  vis_utils.plot_model(model, to_file='model1.png', show_layer_names=False)

tests/keras/utils/vis_utils_test.py:19:

---

keras/utils/vis_utils.py:132: in plot_model dot = model_to_dot(model, show_shapes, show_layer_names, rankdir) keras/utils/vis_utils.py:55: in model_to_dot _check_pydot()

---

def _check_pydot():
    """Raise errors if `pydot` or GraphViz unavailable."""
    if pydot is None:
        raise ImportError(
            'Failed to import `pydot`. '
            'Please install `pydot`. '
            'For example with `pip install pydot`.')
    try:
        # Attempt to create an image of a blank graph
        # to check the pydot/graphviz installation.
        pydot.Dot.create(pydot.Dot())
    except OSError:
        raise OSError(

          '`pydot` failed to call GraphViz.'

'Please install GraphViz (https://www.graphviz.org/) ' 'and ensure that its executables are in the $PATH.') E OSError: pydot failed to call GraphViz.Please install GraphViz (https://www.graphviz.org/) and ensure that its executables are in the $PATH.

Looks like pydot is not getting installed - https://github.com/awslabs/keras-apache-mxnet/pull/177

[roywei]

@kalyc @sandeep-krishnamurthy fixed issues with graphviz and running unit tests at last. Changed both nightly and pr build spec. Tested on code build it's passing now.