Rosdep 导入 python 模块 pyexpat 失败

Question

我正在尝试在 Debian Jessie 上安装 ROS，但在运行 sudo rosdep init 时遇到了错误。我遵循的说明位于此 URL (http://wiki.ros.org/kinetic/Installation/Source)。由于某些库冲突，我是从源代码安装而不是通过他们的存储库安装。

运行 sudo rosdep init 会产生以下输出。

Traceback (most recent call last):
  File "/usr/bin/rosdep", line 3, in <module>
    from rosdep2.main import rosdep_main
  File "/usr/lib/python2.7/dist-packages/rosdep2/__init__.py", line 40, in <module>
    from .installers import InstallerContext, Installer, \
  File "/usr/lib/python2.7/dist-packages/rosdep2/installers.py", line 35, in <module>
    from rospkg.os_detect import OsDetect
  File "/usr/lib/python2.7/dist-packages/rospkg/__init__.py", line 42, in <module>
    from .rospack import expand_to_packages, get_package_name, \
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 35, in <module>
    from xml.etree.cElementTree import ElementTree
  File "/usr/lib/python2.7/xml/etree/cElementTree.py", line 3, in <module>
    from _elementtree import *
ImportError: PyCapsule_Import could not import module "pyexpat"

我认为这是python根本找不到模块，所以我查看了它的位置和python的路径，无济于事。

[jwerner5@rockhopper:~ ] $$ find / -name pyexpat*
/usr/include/python2.7/pyexpat.h
/usr/include/python3.4m/pyexpat.h
/usr/share/jython/Lib/pyexpat.py
/usr/share/jython/Lib/pyexpat$py.class
/usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so

>>> import sys
>>> print sys.path
['', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-x86_64-linux-gnu',
 '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', 
 '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', 
 '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PILcompat',
 '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7',
 '/usr/lib/python2.7/dist-packages/wx-3.0-gtk2']

所以它在路径中。接下来我运行了strace -e open rosdep，只是确保它正在找到文件。这是它的输出。看起来它找到了文件然后立即关闭它。这是相关的部分。

open("/usr/lib/python2.7/lib-tk/pyexpat.py", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib/python2.7/lib-tk/pyexpat.pyc", O_RDONLY) = -1 ENOENT (No such file or directory)
open("/usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so", O_RDONLY) = 9
open("/usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so", O_RDONLY|O_CLOEXEC) = 10
Traceback (most recent call last):

这个问题 (ImportError: PyCapsule_Import could not import module "pyexpat") 建议尝试重命名库或重新安装它。我已经尝试了这两件事，但都没有奏效。有人有什么想法吗？

编辑：自发布以来，根据 forax 的说明，我尝试设置 LD_LIBRARY_PATH，在 python shell 中手动导入 pyexpat，并查看 ldd 的输出以用于 pyexpat。

手动导入pyexpat

    Python 2.7.9 (default, Jun 29 2016, 13:08:31) 
    [GCC 4.9.2] on linux2
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import pyexpat
.

在 pyexpat 库上运行 ldd

[jwerner5@rockhopper:~ ] $$ ldd /usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so
    linux-vdso.so.1 (0x00007ffc069da000)
    libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f7214382000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f7214165000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f7213db9000)
    /lib64/ld-linux-x86-64.so.2 (0x000055fe01ce4000)

Answer 1

请尝试在 python shell 中手动导入并发布结果。

$ python
Python 2.7.9 (default, Jun 29 2016, 13:08:31) 
[GCC 4.9.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import pyexpat
>>> 

并检查 lib 负载，应该如下所示：

$ ldd /usr/lib/python2.7/lib-dynload/pyexpat.x86_64-linux-gnu.so
    linux-vdso.so.1 (0x00007ffe82d10000)
    libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f6387386000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007f6387169000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f6386dbd000)
    /lib64/ld-linux-x86-64.so.2 (0x00005628bbd68000)