Unable to uninstall Drush

Question

I am trying to upgrade drush from version 8 to 10.* but running into problems and will greatly appreciate your help. Please see the error below:

"Installation failed, deleting ./composer.json.

[RuntimeException] No composer.json present in the current directory (./composer.json), this m ay be the cause of the following exception.

[Composer\Downloader\TransportException] curl error 35 while downloading https://repo.packagist.org/packages.json: E ncountered end of file"

Whereis drush shows the "/usr/local/bin/drush". The composer.json file located in "/usr/loca/bin" contents is as follows:

{ "require": { "monolog/monolog": "1.0.*" } }