OK. Just for close this thread … I solved this issue.
Following another thread I did the commands :
brew unlink mariadb
brew install mariadb-connector-c
ln -s /usr/local/opt/mariadb-connector-c/bin/mariadb_config /usr/local/bin/mysql_configpip2 uninstall mysqlclient
pip2 install mysqlclientrm /usr/local/bin/mysql_config
brew unlink mariadb-connector-c
brew link mariadb
But, later I saw that the errors showed in screen are with another path of pip:
./env/bin/pip
So, I did the same commands but pointing to this enviroment …
brew unlink mariadb
brew install mariadb-connector-c
ln -s /usr/local/opt/mariadb-connector-c/bin/mariadb_config /usr/local/bin/mysql_config./env/bin/pip uninstall mysqlclient
./env/bin/pip install mysqlclientrm /usr/local/bin/mysql_config
brew unlink mariadb-connector-c
brew link mariadb
After that I can run almost ok a “bench update” command …
I have another issue , but first at all I’m going to search about that 
Thread Closed I think.