Fix launching non python kernels from a windows store installed jupyter

jupyter_client/manager.py

@@ -191,7 +191,12 @@ def format_kernel_cmd(self, extra_arguments=None):
             # but it should be.
             cmd[0] = sys.executable
 
-        ns = dict(connection_file=self.connection_file,
+        # Make sure to use the realpath for the connection_file
+        # On windows, when running with the store python, the connection_file path
+        # is not usable by non python kernels because the path is being rerouted when
+        # inside of a store app.
+        # See this bug here: https://bugs.python.org/issue41196
+        ns = dict(connection_file=os.path.realpath(self.connection_file),
                   prefix=sys.prefix,
                  )
 

jupyter_client/tests/test_manager.py

@@ -0,0 +1,38 @@
+"""Tests for KernelManager"""
+
+# Copyright (c) Jupyter Development Team.
+# Distributed under the terms of the Modified BSD License.
+
+from jupyter_client.kernelspec import KernelSpec
+from unittest import mock
+from jupyter_client.manager import KernelManager
+import os
+import tempfile
+
+
+def test_connection_file_real_path():
+    """ Verify realpath is used when formatting connection file """
+    with mock.patch('os.path.realpath') as patched_realpath:
+        patched_realpath.return_value = 'foobar'
+        km = KernelManager(connection_file=os.path.join(
+                tempfile.gettempdir(), "kernel-test.json"),
+                kernel_name='test_kernel')
+
+        # KernelSpec and launch args have to be mocked as we don't have an actual kernel on disk
+        km._kernel_spec = KernelSpec(resource_dir='test', 
+            **{
+                "argv": [
+                    "python.exe",
+                    "-m",
+                    "test_kernel",
+                    "-f",
+                    "{connection_file}"
+                ],
+                "env": {},
+                "display_name": "test_kernel",
+                "language": "python",
+                "metadata": {}
+            })
+        km._launch_args = {}
+        cmds = km.format_kernel_cmd()
+        assert cmds[4] is 'foobar'