catkin_make , python-catkin-pkg doesn't work,

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hwlee@hwlee:~/catkin_ws$ catkin_make

Command 'catkin_make' not found, but can be installed with:

sudo apt install catkin

hwlee@hwlee:~/catkin_ws$ sudo apt install catkin

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:


 catkin : Depends: python-catkin-pkg but it is not going to be installed

E: Unable to correct problems, you have held broken packages.

hwlee@hwlee:~/catkin_ws$ sudo apt-get install python-catkin-pkg

Reading package lists... Done
Building dependency tree       
Reading state information... Done
python-catkin-pkg is already the newest version (0.4.15-100).

0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

I installed ros-melodic to new computer and have this problem.

How can I solve this one?