[Tex/LaTex] How to use textopenbullet character for the nested itemize lists

Question

I will use \textopenbullit symbol for all secods level lists in my document:

\documentclass[a4paper,12pt]{article}

\usepackage{cmap}
\usepackage{mathtext}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}         
\frenchspacing
\usepackage{csquotes}
\usepackage{float}
\usepackage{wrapfig}

\renewcommand{\labelitemii}{$\textopenbullet$}

\begin{document}

\begin{itemize} 
\item Bla bla
     \begin{itemize} 
        \item Bla bla bla
        \item ...
     \end{itemize}
\item aaa
\item bbb
\end{itemize}

\end{document}

But I get an error for every line with an list item:

Command \textopenbullet unavailable in encoding OT1.

What is OT1 (I don't use this package) and how can I fix this problem?

(When I use for example \renewcommand{\labelitemii}{$\star$} always is good.)

Answer 1

With enumitem

\documentclass[a4paper,12pt]{article}

\usepackage{textcomp}
\usepackage{enumitem}

\setlist[itemize,2]{label=\textopenbullet}

\begin{document}

\begin{itemize}
\item Bla bla
     \begin{itemize}
        \item Bla bla bla
        \item ...
     \end{itemize}
\item aaa
\item bbb
\end{itemize}

\end{document}