! LaTeX Error: Command \printglossary already defined.

Recently, I had reason to insert some Chinese characters in to the main body of text of a memoir-based LuaLaTeX document. The unicode characters were already in the document so it seemed like a case of getting them correctly translated into a fonts that supports them. XeTeX has some dedicated packages for this, and after some rooting around at CTAN came across a luatexja. This package does a similar job for LuaLaTex, and takes care of the kerning, tracking etc.

Add the following to the preamble,

\usepackage{luatexja-fontspec}
\setmainjfont{FandolSong}

However, since there is a redefinition of \printglossary, it is necessary to mute this with \let\printglossary\relax prior to calling the package. So,

\let\printglossary\relax
\usepackage{luatexja-fontspec}
\setmainjfont{FandolSong}