[BUG] AttributeError: '_Printer' object has no attribute 'split' in rfc822_escape

setuptools version

57.4.0

Python version

3.8.11

OS

OSX (Docker image python:3.8)

Additional environment information

I suspect https://github.com/pypa/setuptools/pull/2640/files triggered it. 56.2.0 fails. 56.1.0 works.

Description

My setup.py is

setup(
    name=name,
    version=version,
    packages=['REDACTED'],
    author=author,
    author_email=author_email,
    classifiers=[
        'Development Status :: Release',
        'Intended Audience :: Developers',
        'Topic :: Utilities',
        'Natural Language :: English',
        'License :: Private Domain',
        'Operating System :: Linux',
        'Programming Language :: Python :: 3.7'
    ],
    description=description,
    install_requires=install_requirements,
    long_description=readme,
    include_package_data=True,
    setup_requires=['setuptools_scm'],
    license=license,
    keywords=['REDACTED', 'REDACTED', 'REDACTED', 'REDACTED', 'REDACTED'],
    url=url,
    zip_safe=False,
    entry_points={
        'console_scripts': [
            "REDACTED = REDACTED.cli.cli:cli"
        ]
    }
)

The repository does not have a LICENSE.txt in it.

My version.py has:

__title__ = 'REDACTED'
__description__ = 'REDACTED'
__url__ = 'REDACTED'
__author__ = 'REDACTED'
__author_email__ = 'REDACTED'
__license__ = 'Proprietary'
__copyright__ = 'REDACTED'
__name__ = "REDACTED"
__version__ = '1.10.0'
__final_release__ = False

Build fails as seen in the console output below.

Expected behavior

The build should complete.

How to Reproduce

Build an egg that does not specify a license in license.py, but does in __version__.py as a single line. The build will fail as shown in Output.

Output

writing MYAPP.egg-info/PKG-INFO
Traceback (most recent call last):
  File "setup.py", line 43, in <module>
    setup(
  File "/usr/local/lib/python3.8/site-packages/setuptools/__init__.py", line 153, in setup
    return distutils.core.setup(**attrs)
  File "/usr/local/lib/python3.8/distutils/core.py", line 148, in setup
    dist.run_commands()
  File "/usr/local/lib/python3.8/distutils/dist.py", line 966, in run_commands
    self.run_command(cmd)
  File "/usr/local/lib/python3.8/distutils/dist.py", line 985, in run_command
    cmd_obj.run()
  File "/usr/local/lib/python3.8/site-packages/setuptools/command/sdist.py", line 42, in run
    self.run_command('egg_info')
  File "/usr/local/lib/python3.8/distutils/cmd.py", line 313, in run_command
    self.distribution.run_command(command)
  File "/usr/local/lib/python3.8/distutils/dist.py", line 985, in run_command
    cmd_obj.run()
  File "/usr/local/lib/python3.8/site-packages/setuptools/command/egg_info.py", line 292, in run
    writer(self, ep.name, os.path.join(self.egg_info, ep.name))
  File "/usr/local/lib/python3.8/site-packages/setuptools/command/egg_info.py", line 635, in write_pkg_info
    metadata.write_pkg_info(cmd.egg_info)
  File "/usr/local/lib/python3.8/distutils/dist.py", line 1117, in write_pkg_info
    self.write_pkg_file(pkg_info)
  File "/usr/local/lib/python3.8/site-packages/setuptools/dist.py", line 185, in write_pkg_file
    license = rfc822_escape(self.get_license())
  File "/usr/local/lib/python3.8/distutils/util.py", line 475, in rfc822_escape
    lines = header.split('\n')

Code of Conduct

• I agree to follow the PSF Code of Conduct

[jhmartin]

Setting

    license="Somestring",

in setup.py also works around the issue.

[Mr-ZJH]

useful