python - 安装错误认为pythonpath为空

我正在尝试安装scikits.nufft软件包here
我下载了zip文件，将其解压缩并cd到目录中。它包含一个setup.py文件，所以我运行

python setup.py install

但这给了我以下与我的PYTHONPATH有关的错误

sudo python setup.py install
sudo: unable to resolve host Lenovo
/usr/local/lib/python2.7/dist-packages/distribute-0.6.31-py2.7.egg/setuptools/command/install_scripts.py:3: UserWarning: Module dap was already imported from None, but /usr/lib/python2.7/dist-packages is being added to sys.path
  from pkg_resources import Distribution, PathMetadata, ensure_directory
running install
Checking .pth file support in /usr/local/lib/python2.7/site-packages/
/usr/bin/python -E -c pass
TEST FAILED: /usr/local/lib/python2.7/site-packages/ does NOT support .pth files
error: bad install directory or PYTHONPATH

You are attempting to install a package to a directory that is not
on PYTHONPATH and which Python does not read ".pth" files from.  The
installation directory you specified (via --install-dir, --prefix, or
the distutils default setting) was:

    /usr/local/lib/python2.7/site-packages/

and your PYTHONPATH environment variable currently contains:

    ''

Here are some of your options for correcting the problem:

* You can choose a different installation directory, i.e., one that is
  on PYTHONPATH or supports .pth files

* You can add the installation directory to the PYTHONPATH environment
  variable.  (It must then also be on PYTHONPATH whenever you run
  Python and want to use the package(s) you are installing.)

* You can set up the installation directory to support ".pth" files by
  using one of the approaches described here:

  http://packages.python.org/distribute/easy_install.html#custom-installation-locations

Please make the appropriate changes for your system and try again.

似乎认为路径是空的，但是当我检查路径时，

echo $PYTHONPATH
/usr/local/lib/python2.7/site-packages:/home/david/PYTHON

有谁知道为什么会认为路径是空的？或对此处可能存在的问题有其他任何想法。
谢谢，
戴夫

最佳答案

在上面Aya的评论之后，我发现了类似的已解决问题here并通过添加使其运行

Defaults    env_keep += "PYTHONPATH"

到sudoers文件。
，
戴夫