QtCharts in Qt Designer

[igorr]

Hi everybody,
again I am facing a problem with adding an external element to Qt Designer via promoting basic classes.
Now I have a problem with promoting QtChart...
May be this is just some problem with my understanding of how the promotion works, but I really wasn't able to find any clear instructions on how to do it. May be I am missing some important insight.
With my setup I get an error:

ModuleNotFoundError: No module named 'QtCharts'

Below some basic code example, the according .ui file and a screenshot of installed packages (to assure you that PyQt5 and PyQtChart do have the the same version)

When trying to promote the GraphicsView class I was referring to the following answer on stackoverflow: https://stackoverflow.com/a/48363007/14326459 (Option 1)
The only thing I didn't do is to add QT += charts in the .pro, because I don't quite get what is meant by that.

import sys, os

from PyQt5.uic import loadUi
from PyQt5.QtWidgets import QApplication, QMainWindow

CURRENT_DIRECTORY = os.path.dirname(os.path.realpath(__file__))


class MainWindow(QMainWindow):

    def __init__(self, parent=None):
        super(MainWindow, self).__init__(parent)

        path = os.path.join(CURRENT_DIRECTORY, 'GUI', 'main.ui')
        self.w = loadUi(path)
        self.w.show()


if __name__ == '__main__':

    app = QApplication(sys.argv)
    w = MainWindow()
    sys.exit(app.exec_())

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>670</width>
    <height>403</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
   <widget class="QChartView" name="graphicsView">
    <property name="geometry">
     <rect>
      <x>90</x>
      <y>60</y>
      <width>256</width>
      <height>192</height>
     </rect>
    </property>
   </widget>
  </widget>
  <widget class="QMenuBar" name="menubar">
   <property name="geometry">
    <rect>
     <x>0</x>
     <y>0</y>
     <width>670</width>
     <height>21</height>
    </rect>
   </property>
  </widget>
  <widget class="QStatusBar" name="statusbar"/>
 </widget>
 <customwidgets>
  <customwidget>
   <class>QChartView</class>
   <extends>QGraphicsView</extends>
   <header>QtCharts</header>
  </customwidget>
 </customwidgets>
 <resources/>
 <connections/>
 <buttongroups>
  <buttongroup name="abc"/>
 </buttongroups>
</ui>

Thanks a lot in advance for all your answers!