Factor out the ipython implementation in ipynb_exporter

The internal ABI for ipython has changed between ipython version 2 and
3.  In its current state, the result processor only works with IPython
version 2, so fail if the user wants to use the result processor with
the wrong version.

Abstract the ipython interface to a file so that we can make it support
versions 2 and 3 at the same time.

wlauto/utils/ipython.py

@@ -0,0 +1,130 @@
+#    Copyright 2015 ARM Limited
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import os
+import subprocess
+
+import_error_str = ''
+try:
+    import IPython
+except ImportError as import_error:
+    IPython = None
+    # Importing IPython can fail for a variety of reasons, report the actual
+    # failure unless it's just that the package is not present
+    if import_error.message.startswith("No module named"):  # pylint: disable=E1101
+        import_error_str = 'ipynb_exporter requires ipython package to be installed'
+    else:
+        import_error_str = import_error.message
+
+if IPython and (IPython.version_info[0] == 2):
+    import IPython.kernel
+    import IPython.nbformat.current
+
+    def read_notebook(notebook_in):
+        return IPython.nbformat.current.reads_json(notebook_in)
+
+    def write_notebook(notebook, fout):
+        IPython.nbformat.current.write(notebook, fout, 'json')
+
+    NotebookNode = IPython.nbformat.current.NotebookNode
+
+elif IPython:
+    # Unsupported IPython version
+    IPython_ver_str = ".".join([str(n) for n in IPython.version_info])
+    import_error_str = 'Unsupported IPython version {}'.format(IPython_ver_str)
+
+
+def run_cell(kernel_client, cell):
+    """Run a cell of a notebook in an ipython kernel and return its output"""
+    kernel_client.shell_channel.execute(cell.input)
+
+    outs = []
+    while True:
+        msg = kernel_client.get_iopub_msg()
+
+        msg_type = msg["msg_type"]
+        content = msg["content"]
+        out = NotebookNode(output_type=msg_type)
+
+        if msg_type == "status":
+            if content["execution_state"] == "idle":
+                break
+            else:
+                continue
+        elif msg_type == "pyin":
+            continue
+        elif msg_type == "stream":
+            out.stream = content["name"]
+            out.text = content["data"]
+        elif msg_type in ("display_data", "pyout"):
+            for mime, data in content["data"].iteritems():
+                if mime == "text/plain":
+                    attr = "text"
+                else:
+                    attr = mime.split("/")[-1]
+                setattr(out, attr, data)
+        elif msg_type == "pyerr":
+            out.ename = content["ename"]
+            out.evalue = content["evalue"]
+            out.traceback = content["traceback"]
+        else:
+            raise ValueError("Unknown msg_type {}".format(msg_type))
+
+        outs.append(out)
+
+    return outs
+
+
+def run_notebook(notebook):
+    """Run the notebook"""
+
+    kernel_manager = IPython.kernel.KernelManager()
+    kernel_manager.start_kernel(stderr=open(os.devnull, 'w'))
+    kernel_client = kernel_manager.client()
+    kernel_client.start_channels()
+
+    for sheet in notebook.worksheets:
+        for (prompt_number, cell) in enumerate(sheet.cells, 1):
+            if cell.cell_type != "code":
+                continue
+
+            cell.outputs = run_cell(kernel_client, cell)
+
+            cell.prompt_number = prompt_number
+            if cell.outputs:
+                cell.outputs[0]["prompt_number"] = prompt_number
+
+    kernel_manager.shutdown_kernel()
+
+
+def generate_pdf(nbbasename, output_directory):
+    """Generate a PDF from the ipython notebook
+
+    ipython nbconvert claims that the CLI is not stable, so keep this
+    function here to be able to cope with inconsistencies
+
+    """
+
+    prev_dir = os.getcwd()
+    os.chdir(output_directory)
+
+    ipython_nbconvert = ['ipython', 'nbconvert', '--to=latex', '--post=PDF',
+                         nbbasename]
+
+    with open(os.devnull, 'w') as devnull:
+        subprocess.check_call(ipython_nbconvert, stderr=devnull)
+
+    os.chdir(prev_dir)
+