From: http://pyqt.sourceforge.net/Docs/PyQt5/pyqt4_differences.html there seems to be no more pyqtconfig module in PyQt5:

pyqtconfig Module

PyQt4’s pyqtconfig module is not supported. The section The PyQt5 Extension API describes the support that PyQt5 provides to third-party packages (e.g. QScintilla) that want to build on top of PyQt5.

So it's not possible to compile QGIS 3.2 from sources on Ubuntu (16.04) because it's used by the file FindPyQt5.py in the cmake folder:

https://github.com/qgis/QGIS/blob/master/cmake/FindPyQt5.py

cd /opt/QGIS/build3_2/
cat ../cmake/FindPyQt5.py | grep -in pyqtconfig
    34:    import PyQt5.pyqtconfig
    35:    pyqtcfg = PyQt5.pyqtconfig.Configuration()

The compilation process ends on:

Traceback (most recent call last):
  File "/opt/QGIS/cmake/FindPyQt5.py", line 34, in <module>
    import PyQt5.pyqtconfig
ImportError: No module named 'PyQt5.pyqtconfig'

Is there any solution or workaround?

From: http://pyqt.sourceforge.net/Docs/PyQt5/pyqt4_differences.html there seems to be no more pyqtconfig module in PyQt5:

pyqtconfig Module

PyQt4’s pyqtconfig module is not supported. The section The PyQt5 Extension API describes the support that PyQt5 provides to third-party packages (e.g. QScintilla) that want to build on top of PyQt5.

So it's not possible to compile QGIS 3.2 from sources on Ubuntu (16.04) because it's used by the file FindPyQt5.py in the cmake folder:

https://github.com/qgis/QGIS/blob/master/cmake/FindPyQt5.py

cd /opt/QGIS/build3_2/
cat ../cmake/FindPyQt5.py | grep -in pyqtconfig
    34:    import PyQt5.pyqtconfig
    35:    pyqtcfg = PyQt5.pyqtconfig.Configuration()

The compilation process ends on:

Traceback (most recent call last):
  File "/opt/QGIS/cmake/FindPyQt5.py", line 34, in <module>
    import PyQt5.pyqtconfig
ImportError: No module named 'PyQt5.pyqtconfig'

My PyQt5 version is 5.11.2.

Is there any solution or workaround?