Spyder should depend on QtWebEngine for pyqt >= 5.12

[jenshnielsen]

In PyQt5.12 the QtWebEngine has been split out into its own pypi package see
https://www.riverbankcomputing.com/news/pyqt-512 but spyder does not depend on it so a new pip install of spyder fails on launch.

Issue Report Checklist

• Searched the issues page for similar reports
• Read the relevant sections of the Spyder Troubleshooting Guide and followed its advice
• Reproduced the issue after updating with conda update spyder (or pip, if not using Anaconda)
• Completed the Problem Description, Steps to Reproduce and Version sections below

Problem Description

What steps reproduce the problem?

In a clean env without pyqt or spyder installed

1. pip install spyder
2. spyder3.exe

What is the expected output? What do you see instead?

Traceback (most recent call last):
  File "c:\users\jenielse\appdata\local\continuum\miniconda3\envs\mypipenv\lib\site-packages\qtpy\QtWebEngineWidgets.py", line 22, in <module>
    from PyQt5.QtWebEngineWidgets import QWebEnginePage
ModuleNotFoundError: No module named **'PyQt5.QtWebEngineWidgets'**

pip install pyqtwebengine fixes the issue and spyder launches normally

Versions

• Spyder version: 3.3.3
• Python version: 3.6.8
• Qt version: 5.12
• PyQt version: 5.12
• Operating System name/version: Windows 10

[ccordoba12]

We didn't know that was going to happen, else we'll have added it as a dependency in our 3.3.3 release. But we'll fix it for 3.3.4.