A11y_AzureNotebooks_Jupyter_EditMetada_Keyboard: Keyboard focus does not go to 'Close' button of the Popup.

[AccessibilityTestingTeam-TCS]

Environment Details:
Application Name: AzureNotebooks_Jupyter
Login URL: notebooks.azure.com
Browser Details:
Edge: Microsoft Edge 42.17134.1.0
Chrome: Version 68.0.3440.106
Operating System:Windows10

Steps to reproduce:
1.Login with the appropriate credentials to azure notebook account.
2.Go to Get started à libraries à Select any of the libraries à click on clone to clone the library
3.Click on Run or right click and select Run to run the notebook.
4.Navigate to any file present under Files tab-->Hit enter-->View Menu-->Cell Toolbar-->Edit Metadata. Click on Edit Metadata button appeared on page.
5. Try to navigate to 'Close' button of the pop-up using keyboard.

Actual:
Keyboard focus does not go to 'Close' button of the Popup.

This issue exist for 'Chrome + NVDA' configuration also.

Note:
Same issue is observed in below pages:

1. MoveConfirmationPopup: Navigate to run button & hit enter --> select any file --> navigate to Move button & hit enter.

Expected:
Keyboard focus should go to 'Close' button of the Popup.

User Impact:
Keyboard only user will not be access the 'Close' button present on the Popup.

Attachment:
(https://github.com/jupyter/notebook/files/2401275/A11y_AzureNotebooks_Jupyter_EditMetada_Keyboard.pptx)

[jtpio]

Closing as there are now different issues tracking accessibility improvements for Jupyter Notebook 7, for example #6800

Thanks!