Install libqscintilla2-qt4-dev by entering the following commands in the terminal:
sudo apt update sudo apt install libqscintilla2-qt4-dev
Scintilla source code editing widget for Qt4, development files
QScintilla is a text editor for Qt4 with features especially useful when writing and debugging source code. These include support for syntax styling, error indicators, code completion, call tips and margins. . This package contains development headers needed when developing C++ applications that use QScintilla 2.