I understand that you have already created a Build System that runs Python 3 but you need to configure SublimeREPL to do the same. I use mac but I imagine that the process can be the same.
What you have to do is look for the file Main.sublime-menu in "Sublime Text 3 -> Packages -> SublimeREPL - > config -> Python" and change the code it contains to the following:
[
{
"id": "tools",
"children":
[{
"caption": "SublimeREPL",
"mnemonic": "r",
"id": "SublimeREPL",
"children":
[
{"caption": "Python",
"id": "Python",
"children":[
{"command": "repl_open",
"caption": "Python",
"id": "repl_python",
"mnemonic": "p",
"args": {
"type": "subprocess",
"encoding": "utf8",
"cmd": ["python3", "-i", "-u"],
"cwd": "$file_path",
"syntax": "Packages/Python/Python.tmLanguage",
"external_id": "python",
"extend_env": {"PYTHONIOENCODING": "utf-8"}
}
},
{"command": "python_virtualenv_repl",
"id": "python_virtualenv_repl",
"caption": "Python - virtualenv"},
{"command": "repl_open",
"caption": "Python - PDB current file",
"id": "repl_python_pdb",
"mnemonic": "d",
"args": {
"type": "subprocess",
"encoding": "utf8",
"cmd": ["python3", "-i", "-u", "-m", "pdb", "$file_basename"],
"cwd": "$file_path",
"syntax": "Packages/Python/Python.tmLanguage",
"external_id": "python",
"extend_env": {"PYTHONIOENCODING": "utf-8"}
}
},
{"command": "repl_open",
"caption": "Python - RUN current file",
"id": "repl_python_run",
"mnemonic": "d",
"args": {
"type": "subprocess",
"encoding": "utf8",
"cmd": ["python3", "-u", "$file_basename"],
"cwd": "$file_path",
"syntax": "Packages/Python/Python.tmLanguage",
"external_id": "python",
"extend_env": {"PYTHONIOENCODING": "utf-8"}
}
},
{"command": "repl_open",
"caption": "Python - IPython",
"id": "repl_python_ipython",
"mnemonic": "p",
"args": {
"type": "subprocess",
"encoding": "utf8",
"autocomplete_server": true,
"cmd": {
"osx": ["python", "-u", "${packages}/SublimeREPL/config/Python/ipy_repl.py"],
"linux": ["python3", "-u", "${packages}/SublimeREPL/config/Python/ipy_repl.py"],
"windows": ["python", "-u", "${packages}/SublimeREPL/config/Python/ipy_repl.py"]
},
"cwd": "$file_path",
"syntax": "Packages/Python/Python.tmLanguage",
"external_id": "python",
"extend_env": {
"PYTHONIOENCODING": "utf-8",
"SUBLIMEREPL_EDITOR": "$editor"
}
}
}
]}
]
}]
}]
If you still have problems maybe this video can help you:
Tutorial configuration SublimeREPL to run Python 3
I hope that my answer has been useful, luck
Greetings
