Dlibのインストールでエラーが出るときの対処（Ubuntu)

# 環境

- WSL Ubuntu 18.04
-  Python3 3.8.5

# エラー
(全文)

```bash
    Running setup.py install for dlib ... error
    ERROR: Command errored out with exit status 1:
     command: /usr/bin/python3 -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-3kh7uz0l/dlib/setup.py'"'"'; __file__='"'"'/tmp/pip-install-3kh7uz0l/dlib/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-za_imyet/install-record.txt --single-version-externally-managed --user --prefix= --compile --install-headers /home/oae/.local/include/python3.8/dlib
         cwd: /tmp/pip-install-3kh7uz0l/dlib/
    Complete output (55 lines):
    running install
    running build
    running build_py
    package init file 'tools/python/dlib/__init__.py' not found (or not a regular file)
    running build_ext
    Traceback (most recent call last):
      File "/tmp/pip-install-3kh7uz0l/dlib/setup.py", line 120, in get_cmake_version
        out = subprocess.check_output(['cmake', '--version'])
      File "/usr/lib/python3.8/subprocess.py", line 411, in check_output
        return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
      File "/usr/lib/python3.8/subprocess.py", line 489, in run
        with Popen(*popenargs, **kwargs) as process:
      File "/usr/lib/python3.8/subprocess.py", line 854, in __init__
        self._execute_child(args, executable, preexec_fn, close_fds,
      File "/usr/lib/python3.8/subprocess.py", line 1702, in _execute_child
        raise child_exception_type(errno_num, err_msg, err_filename)
    FileNotFoundError: [Errno 2] No such file or directory: 'cmake'

    During handling of the above exception, another exception occurred:

    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      File "/tmp/pip-install-3kh7uz0l/dlib/setup.py", line 223, in <module>
        setup(
      File "/usr/lib/python3/dist-packages/setuptools/__init__.py", line 144, in setup
        return distutils.core.setup(**attrs)
      File "/usr/lib/python3.8/distutils/core.py", line 148, in setup
        dist.run_commands()
      File "/usr/lib/python3.8/distutils/dist.py", line 966, in run_commands
        self.run_command(cmd)
      File "/usr/lib/python3.8/distutils/dist.py", line 985, in run_command
        cmd_obj.run()
      File "/usr/lib/python3/dist-packages/setuptools/command/install.py", line 61, in run
        return orig.install.run(self)
      File "/usr/lib/python3.8/distutils/command/install.py", line 589, in run
        self.run_command('build')
      File "/usr/lib/python3.8/distutils/cmd.py", line 313, in run_command
        self.distribution.run_command(command)
      File "/usr/lib/python3.8/distutils/dist.py", line 985, in run_command
        cmd_obj.run()
      File "/usr/lib/python3.8/distutils/command/build.py", line 135, in run
        self.run_command(cmd_name)
      File "/usr/lib/python3.8/distutils/cmd.py", line 313, in run_command
        self.distribution.run_command(command)
      File "/usr/lib/python3.8/distutils/dist.py", line 985, in run_command
        cmd_obj.run()
      File "/tmp/pip-install-3kh7uz0l/dlib/setup.py", line 129, in run
        cmake_version = self.get_cmake_version()
      File "/tmp/pip-install-3kh7uz0l/dlib/setup.py", line 122, in get_cmake_version
        raise RuntimeError("\n*******************************************************************\n" +
    RuntimeError:
    *******************************************************************
     CMake must be installed to build the following extensions: _dlib_pybind11
    *******************************************************************

    ----------------------------------------


ERROR: Command errored out with exit status 1: /usr/bin/python3 -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-3kh7uz0l/dlib/setup.py'"'"'; __file__='"'"'/tmp/pip-install-3kh7uz0l/dlib/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-za_imyet/install-record.txt --single-version-externally-managed --user --prefix= --com
```
#原因

- Cmakeがインストールされていない

#修正

```
sudo apt install cmake
```

:)