Catkin_make problem with xacro when installing gazebo

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I encountered a problem of xacro when I am trying to install gazebo. which is

CMake Error at /opt/ros/groovy/share/catkin/cmake/catkinConfig.cmake:72 (find_package): CMake Error at /opt/ros/groovy/share/catkin/cmake/catkinConfig.cmake:72 (find_package): Could not find a configuration file for package xacro.

Set xacro_DIR to the directory containing a CMake configuration file for xacro. The file will have one of the following names:

xacroConfig.cmake
xacro-config.cmake

I tried to install xacro via ros wiki using "git clone -b". And it was successfully installed. However the problem still exists. And I have no idea what to do now. If I try to reinstall the xacro, it will show : fatal: destination path 'xacro' already exists and is not an empty directory.