Open your package folder (Preferences > Browse packages) and create a file named Python (VirtualEnvWrapper).sublime-build. That will be our build system.
WARNING: Make sure your sublime project name is the same as virtualenvwrapper project name!
Now copy-paste the following JSON:
{
"shell_cmd": "~/.virtualenvs/$project_base_name/bin/python3 -u \"$file\"",
"path": "$project_path",
"file_regex": "^[ ]File "(...?)", line ([0-9]*)",