#!/usr/bin/env python3

# tsuserver3, an Attorney Online server
#
# Copyright (C) 2016 argoneus <argoneuscze@gmail.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from server.tsuserver import TsuServer3

# Idiotproof setup
def check_pyyaml():
    try:
        import yaml
    except ImportError:
        print("Couldn't import PyYAML. Installing it for you...")
        import pip
        pip.main(["install", "--user", "pyyaml"])

def main():
    server = TsuServer3()
    server.start()


if __name__ == '__main__':
    check_pyyaml()
    main()

#!/usr/bin/env python3

# tsuserver3, an Attorney Online server
#
# Copyright (C) 2016 argoneus <argoneuscze@gmail.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

from server.tsuserver import TsuServer3

# Idiotproof setup
def check_pyyaml():
    try:
        import yaml
    except ModuleNotFoundError:
        print("Couldn't import PyYAML. Installing it for you...")
        import pip
        pip.main(["install", "--user", "pyyaml"])

def main():
    server = TsuServer3()
    server.start()


if __name__ == '__main__':
    check_pyyaml()
    main()

Use ModuleNotFoundError instead of ImportError