执行：sudo apt-get install python-pip python-dev
报错如下：
The following packages have unmet dependencies:
python-dev : Depends: libpython-dev (= 2.7.11-1) but it is not going to be installed
Depends: python2.7-dev (>= 2.7.11-1~) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
解决方法：使用aptitude 工具
sudo apt-get install aptitude
然后：sudo aptitude install python-dev
The following NEW packages will be installed:
libpython-dev{a} libpython2.7-dev{ab} python-dev python2.7-dev{ab}
。。。
4) python2.7-dev [Not Installed]
Accept this solution? [Y/n/q/?] n
The following actions will resolve these dependencies:
Downgrade the following packages:
1) libpython2.7 [2.7.12-1ubuntu0~16.04.2 (now) -> 2.7.11-7ubuntu1 (xenial)]
2) libpython2.7-minimal [2.7.12-1ubuntu0~16.04.2 (now) -> 2.7.11-7ubuntu1 (x
3) libpython2.7-stdlib [2.7.12-1ubuntu0~16.04.2 (now) -> 2.7.11-7ubuntu1 (xe
4) python2.7 [2.7.12-1ubuntu0~16.04.2 (now) -> 2.7.11-7ubuntu1 (xenial)]
5) python2.7-minimal [2.7.12-1ubuntu0~16.04.2 (now) -> 2.7.11-7ubuntu1 (xeni
Accept this solution? [Y/n/q/?] y
The following packages will be DOWNGRADED:
libpython2.7 libpython2.7-minimal libpython2.7-stdlib python2.7
。。。
Do you want to continue? [Y/n/?] y
W: Target Packages (main/binary-amd64/Packages) is configured multiple times in /etc/apt/sources.list.d/precise-updates.list:1 and /etc/apt/sources.list.d/precise-updates.list:2
。。。
Setting up python2.7-dev (2.7.11-7ubuntu1) ...
Setting up python-dev (2.7.11-1) ...
Processing triggers for libc-bin (2.23-0ubuntu10) ...
搞定了，可以执行sudo apt-get install python-pip python-dev了
