prompt: We are currently solving the following issue within our repository. Here is the issue text:
  --- BEGIN ISSUE ---
  Tornado 5.0 raises error on install with older Python versions.
  changed to `"tornado>=4.1,<5.0"` in setup.py
  
  This broke installation via pip for me. 
  
  --- END ISSUE ---
  
  Below are some code segments, each from a relevant file. One or more of these files may contain bugs.
  --- BEGIN FILES ---
  Path: `setup.py`
  Content:
  ```
  1 #!/usr/bin/env python
  2 # -*- coding: utf-8 -*-
  3 
  4 from __future__ import print_function
  5 from setuptools import setup
  6 import re
  7 import os
  8 import sys
  9 
  10 
  11 long_description = (
  12     "MkDocs is a fast, simple and downright gorgeous static site generator "
  13     "that's geared towards building project documentation. Documentation "
  14     "source files are written in Markdown, and configured with a single YAML "
  15     "configuration file."
  16 )
  17 
  18 
  19 def get_version(package):
  20     """Return package version as listed in `__version__` in `init.py`."""
  21     init_py = open(os.path.join(package, '__init__.py')).read()
  22     return re.search("__version__ = ['\"]([^'\"]+)['\"]", init_py).group(1)
  23 
  24 
  25 def get_packages(package):
  26     """Return root package and all sub-packages."""
  27     return [dirpath
  28             for dirpath, dirnames, filenames in os.walk(package)
  29             if os.path.exists(os.path.join(dirpath, '__init__.py'))]
  30 
  31 
  32 if sys.argv[-1] == 'publish':
  33     if os.system("pip freeze | grep wheel"):
  34         print("wheel not installed.\nUse `pip install wheel`.\nExiting.")
  35         sys.exit()
  36     if os.system("pip freeze | grep twine"):
  37         print("twine not installed.\nUse `pip install twine`.\nExiting.")
  38         sys.exit()
  39     os.system("python setup.py sdist bdist_wheel")
  40     os.system("twine upload dist/*")
  41     print("You probably want to also tag the version now:")
  42     print("  git tag -a {0} -m 'version {0}'".format(get_version("mkdocs")))
  43     print("  git push --tags")
  44     sys.exit()
  45 
  46 
  47 setup(
  48     name="mkdocs",
  49     version=get_version("mkdocs"),
  50     url='http://www.mkdocs.org',
  51     license='BSD',
  52     description='Project documentation with Markdown.',
  53     long_description=long_description,
  54     author='Tom Christie',
  55     author_email='tom@tomchristie.com',  # SEE NOTE BELOW (*)
  56     packages=get_packages("mkdocs"),
  57     include_package_data=True,
  58     install_requires=[
  59         'click>=3.3',
  60         'Jinja2>=2.7.1',
  61         'livereload>=2.5.1',
  62         'Markdown>=2.3.1',
  63         'PyYAML>=3.10',
  64         'tornado>=4.1',
  65     ],
  66     entry_points={
  67         'console_scripts': [
  68             'mkdocs = mkdocs.__main__:cli',
  69         ],
  70         'mkdocs.themes': [
  71             'mkdocs = mkdocs.themes.mkdocs',
  72             'readthedocs = mkdocs.themes.readthedocs',
  73         ],
  74         'mkdocs.plugins': [
  75             'search = mkdocs.contrib.search:SearchPlugin',
  76         ],
  77     },
  78     classifiers=[
  79         'Development Status :: 5 - Production/Stable',
  80         'Environment :: Console',
  81         'Environment :: Web Environment',
  82         'Intended Audience :: Developers',
  83         'License :: OSI Approved :: BSD License',
  84         'Operating System :: OS Independent',
  85         'Programming Language :: Python',
  86         'Programming Language :: Python :: 2',
  87         'Programming Language :: Python :: 2.7',
  88         'Programming Language :: Python :: 3',
  89         'Programming Language :: Python :: 3.3',
  90         'Programming Language :: Python :: 3.4',
  91         'Programming Language :: Python :: 3.5',
  92         'Programming Language :: Python :: 3.6',
  93         "Programming Language :: Python :: Implementation :: CPython",
  94         "Programming Language :: Python :: Implementation :: PyPy",
  95         'Topic :: Documentation',
  96         'Topic :: Text Processing',
  97     ],
  98     zip_safe=False,
  99 )
  100 
  101 # (*) Please direct queries to the discussion group:
  102 #     https://groups.google.com/forum/#!forum/mkdocs
  103
  ```
  --- END FILES ---
  
  Please first localize the bug based on the issue statement, and then generate a patch according to the `git diff` format fenced by three backticks.
  
  Here is an example:
  
  ```diff
  diff --git a/examples/server_async.py b/examples/server_async.py
  --- a/examples/server_async.py
  +++ b/examples/server_async.py
  @@ -313,4 +313,4 @@
   
   
   if __name__ == "__main__":
  -    asyncio.run(run_async_server("."), debug=True)
  +    asyncio.run(run_async_server(), debug=True)
  diff --git a/examples/server_sync.py b/examples/server_sync.py
  --- a/examples/server_sync.py
  +++ b/examples/server_sync.py
  @@ -313,5 +313,5 @@
   
   
   if __name__ == "__main__":
  -    server = run_sync_server(".")
  +    server = run_sync_server()
       server.shutdown()
  
  ```
  
golden_diff: diff --git a/setup.py b/setup.py
  --- a/setup.py
  +++ b/setup.py
  @@ -61,8 +61,9 @@
           'livereload>=2.5.1',
           'Markdown>=2.3.1',
           'PyYAML>=3.10',
  -        'tornado>=4.1',
  +        'tornado>=5.0',
       ],
  +    python_requires='>=2.7.9,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',
       entry_points={
           'console_scripts': [
               'mkdocs = mkdocs.__main__:cli',
  @@ -86,7 +87,6 @@
           'Programming Language :: Python :: 2',
           'Programming Language :: Python :: 2.7',
           'Programming Language :: Python :: 3',
  -        'Programming Language :: Python :: 3.3',
           'Programming Language :: Python :: 3.4',
           'Programming Language :: Python :: 3.5',
           'Programming Language :: Python :: 3.6',
  
verification_info: {"golden_diff": "diff --git a/setup.py b/setup.py\n--- a/setup.py\n+++ b/setup.py\n@@ -61,8 +61,9 @@\n         'livereload>=2.5.1',\n         'Markdown>=2.3.1',\n         'PyYAML>=3.10',\n-        'tornado>=4.1',\n+        'tornado>=5.0',\n     ],\n+    python_requires='>=2.7.9,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',\n     entry_points={\n         'console_scripts': [\n             'mkdocs = mkdocs.__main__:cli',\n@@ -86,7 +87,6 @@\n         'Programming Language :: Python :: 2',\n         'Programming Language :: Python :: 2.7',\n         'Programming Language :: Python :: 3',\n-        'Programming Language :: Python :: 3.3',\n         'Programming Language :: Python :: 3.4',\n         'Programming Language :: Python :: 3.5',\n         'Programming Language :: Python :: 3.6',\n", "issue": "Tornado 5.0 raises error on install with older Python versions.\nchanged to `\"tornado>=4.1,<5.0\"` in setup.py\r\n\r\nThis broke installation via pip for me. \n", "before_files": [{"content": "#!/usr/bin/env python\n# -*- coding: utf-8 -*-\n\nfrom __future__ import print_function\nfrom setuptools import setup\nimport re\nimport os\nimport sys\n\n\nlong_description = (\n    \"MkDocs is a fast, simple and downright gorgeous static site generator \"\n    \"that's geared towards building project documentation. Documentation \"\n    \"source files are written in Markdown, and configured with a single YAML \"\n    \"configuration file.\"\n)\n\n\ndef get_version(package):\n    \"\"\"Return package version as listed in `__version__` in `init.py`.\"\"\"\n    init_py = open(os.path.join(package, '__init__.py')).read()\n    return re.search(\"__version__ = ['\\\"]([^'\\\"]+)['\\\"]\", init_py).group(1)\n\n\ndef get_packages(package):\n    \"\"\"Return root package and all sub-packages.\"\"\"\n    return [dirpath\n            for dirpath, dirnames, filenames in os.walk(package)\n            if os.path.exists(os.path.join(dirpath, '__init__.py'))]\n\n\nif sys.argv[-1] == 'publish':\n    if os.system(\"pip freeze | grep wheel\"):\n        print(\"wheel not installed.\\nUse `pip install wheel`.\\nExiting.\")\n        sys.exit()\n    if os.system(\"pip freeze | grep twine\"):\n        print(\"twine not installed.\\nUse `pip install twine`.\\nExiting.\")\n        sys.exit()\n    os.system(\"python setup.py sdist bdist_wheel\")\n    os.system(\"twine upload dist/*\")\n    print(\"You probably want to also tag the version now:\")\n    print(\"  git tag -a {0} -m 'version {0}'\".format(get_version(\"mkdocs\")))\n    print(\"  git push --tags\")\n    sys.exit()\n\n\nsetup(\n    name=\"mkdocs\",\n    version=get_version(\"mkdocs\"),\n    url='http://www.mkdocs.org',\n    license='BSD',\n    description='Project documentation with Markdown.',\n    long_description=long_description,\n    author='Tom Christie',\n    author_email='tom@tomchristie.com',  # SEE NOTE BELOW (*)\n    packages=get_packages(\"mkdocs\"),\n    include_package_data=True,\n    install_requires=[\n        'click>=3.3',\n        'Jinja2>=2.7.1',\n        'livereload>=2.5.1',\n        'Markdown>=2.3.1',\n        'PyYAML>=3.10',\n        'tornado>=4.1',\n    ],\n    entry_points={\n        'console_scripts': [\n            'mkdocs = mkdocs.__main__:cli',\n        ],\n        'mkdocs.themes': [\n            'mkdocs = mkdocs.themes.mkdocs',\n            'readthedocs = mkdocs.themes.readthedocs',\n        ],\n        'mkdocs.plugins': [\n            'search = mkdocs.contrib.search:SearchPlugin',\n        ],\n    },\n    classifiers=[\n        'Development Status :: 5 - Production/Stable',\n        'Environment :: Console',\n        'Environment :: Web Environment',\n        'Intended Audience :: Developers',\n        'License :: OSI Approved :: BSD License',\n        'Operating System :: OS Independent',\n        'Programming Language :: Python',\n        'Programming Language :: Python :: 2',\n        'Programming Language :: Python :: 2.7',\n        'Programming Language :: Python :: 3',\n        'Programming Language :: Python :: 3.3',\n        'Programming Language :: Python :: 3.4',\n        'Programming Language :: Python :: 3.5',\n        'Programming Language :: Python :: 3.6',\n        \"Programming Language :: Python :: Implementation :: CPython\",\n        \"Programming Language :: Python :: Implementation :: PyPy\",\n        'Topic :: Documentation',\n        'Topic :: Text Processing',\n    ],\n    zip_safe=False,\n)\n\n# (*) Please direct queries to the discussion group:\n#     https://groups.google.com/forum/#!forum/mkdocs\n", "path": "setup.py"}], "after_files": [{"content": "#!/usr/bin/env python\n# -*- coding: utf-8 -*-\n\nfrom __future__ import print_function\nfrom setuptools import setup\nimport re\nimport os\nimport sys\n\n\nlong_description = (\n    \"MkDocs is a fast, simple and downright gorgeous static site generator \"\n    \"that's geared towards building project documentation. Documentation \"\n    \"source files are written in Markdown, and configured with a single YAML \"\n    \"configuration file.\"\n)\n\n\ndef get_version(package):\n    \"\"\"Return package version as listed in `__version__` in `init.py`.\"\"\"\n    init_py = open(os.path.join(package, '__init__.py')).read()\n    return re.search(\"__version__ = ['\\\"]([^'\\\"]+)['\\\"]\", init_py).group(1)\n\n\ndef get_packages(package):\n    \"\"\"Return root package and all sub-packages.\"\"\"\n    return [dirpath\n            for dirpath, dirnames, filenames in os.walk(package)\n            if os.path.exists(os.path.join(dirpath, '__init__.py'))]\n\n\nif sys.argv[-1] == 'publish':\n    if os.system(\"pip freeze | grep wheel\"):\n        print(\"wheel not installed.\\nUse `pip install wheel`.\\nExiting.\")\n        sys.exit()\n    if os.system(\"pip freeze | grep twine\"):\n        print(\"twine not installed.\\nUse `pip install twine`.\\nExiting.\")\n        sys.exit()\n    os.system(\"python setup.py sdist bdist_wheel\")\n    os.system(\"twine upload dist/*\")\n    print(\"You probably want to also tag the version now:\")\n    print(\"  git tag -a {0} -m 'version {0}'\".format(get_version(\"mkdocs\")))\n    print(\"  git push --tags\")\n    sys.exit()\n\n\nsetup(\n    name=\"mkdocs\",\n    version=get_version(\"mkdocs\"),\n    url='http://www.mkdocs.org',\n    license='BSD',\n    description='Project documentation with Markdown.',\n    long_description=long_description,\n    author='Tom Christie',\n    author_email='tom@tomchristie.com',  # SEE NOTE BELOW (*)\n    packages=get_packages(\"mkdocs\"),\n    include_package_data=True,\n    install_requires=[\n        'click>=3.3',\n        'Jinja2>=2.7.1',\n        'livereload>=2.5.1',\n        'Markdown>=2.3.1',\n        'PyYAML>=3.10',\n        'tornado>=5.0',\n    ],\n    python_requires='>=2.7.9,!=3.0.*,!=3.1.*,!=3.2.*,!=3.3.*',\n    entry_points={\n        'console_scripts': [\n            'mkdocs = mkdocs.__main__:cli',\n        ],\n        'mkdocs.themes': [\n            'mkdocs = mkdocs.themes.mkdocs',\n            'readthedocs = mkdocs.themes.readthedocs',\n        ],\n        'mkdocs.plugins': [\n            'search = mkdocs.contrib.search:SearchPlugin',\n        ],\n    },\n    classifiers=[\n        'Development Status :: 5 - Production/Stable',\n        'Environment :: Console',\n        'Environment :: Web Environment',\n        'Intended Audience :: Developers',\n        'License :: OSI Approved :: BSD License',\n        'Operating System :: OS Independent',\n        'Programming Language :: Python',\n        'Programming Language :: Python :: 2',\n        'Programming Language :: Python :: 2.7',\n        'Programming Language :: Python :: 3',\n        'Programming Language :: Python :: 3.4',\n        'Programming Language :: Python :: 3.5',\n        'Programming Language :: Python :: 3.6',\n        \"Programming Language :: Python :: Implementation :: CPython\",\n        \"Programming Language :: Python :: Implementation :: PyPy\",\n        'Topic :: Documentation',\n        'Topic :: Text Processing',\n    ],\n    zip_safe=False,\n)\n\n# (*) Please direct queries to the discussion group:\n#     https://groups.google.com/forum/#!forum/mkdocs\n", "path": "setup.py"}]}