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
看来，由于我没有从 ppa 安装 beta1 版本的 QT5，所以我无法使用 Ubuntu 组件包。我已经发布了 QT5 版本，现在对安装测试版不感兴趣。有解决方法吗？
The following packages have unmet dependencies:
qt-components-ubuntu : Depends: qtbase but it is not installable
Depends: qtdeclarative but it is not installable
安装预览工具包的说明在这里。我跳过了安装 QT5 的步骤，因为我已经直接从 qt-project.org 获得了更新版本。