有时，当我安装东西时，我会收到如下错误：
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed
E: Unable to correct problems, you have held broken packages.
我该如何解决这个问题？
package-management apt ppa dependencies software-installation
这些都没有安装python-dev，我启动并运行了我的amd64系统，14.04，当我尝试安装wagtail，django cms时，出现错误：
pysass.c:4:20: fatal error: Python.h: No such file or directory
#include <Python.h>
^
compilation terminated.
error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
----------------------------------------
Cleaning up...
Command /usr/bin/python -c "import setuptools, tokenize;__file__='/tmp/pip_build_root/
libsass/setup.py';exec(compile(getattr(tokenize, 'open', open)(__file__).read().replace
('\r\n', '\n'), __file__, 'exec'))" install --record /tmp/pip-ojWg1O-record/install-
record.txt --single-version-externally-managed --compile failed with error code 1 in
/tmp/pip_build_root/libsass
Storing debug log for failure in /home/payload/.pip/pip.log
如何解决此问题并安装软件包？
这是因为缺少Python.h包含在python-dev包中的 c 头文件。
当我尝试上述链接时，它说：
apt-get install python-dev …
Ubuntu 14.04.3。我无法安装 python-dev：
yura@ubuntu:~$ sudo apt-get install python-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
python-dev : Depends: libpython-dev (= 2.7.5-5ubuntu3) but …