Ubuntu – How to install vim-gnome on Ubuntu 19.10

As andol suggests, this is likely a result of the Universe repository component being disabled. Searching the Ubuntu package database for mercurial reveals it's in Universe.

One way to enable the Universe repository is to press Ctrl+Alt+F2 and run software-properties-gtk. In the Ubuntu Software tab, under Downloadable from the Internet, make sure the checkbox for Community-maintained Open Source software (universe) is checked. For more information on enabling Universe, see:

• How do I enable the "Universe" repository?

Then, to install Mercurial, run:

sudo apt-get update && sudo apt-get install mercurial

mercurial can also be installed from the Software Center.

I presume you are trying to install that package using sudo dpkg -i package, well, that normally leads to package dependency problems so normally I suggest the use of gdebi. If you have any problematic package remove it. You can check using sudo apt-get check. Now down to business:

sudo apt-get install gdebi-core

With that we have ready gdebi. Now if you use a 64-bit system you may like to install the 64-bit package, likewise with 32-bits.

Now here comes the funny stuff...

sudo gdebi graphviz_2.37.20140208.0545-1\~saucy_amd64.deb 
Reading package lists... Done
Building dependency tree        
Reading state information... Done
Building data structures... Done 
Building data structures... Done 
This package is uninstallable
Dependency is not satisfiable: libgd2-noxpm (>= 2.0.36~rc1~dfsg)|libgd2-xpm (>= 2.0.36~rc1~dfsg)

And here is where you stop. The reason is that the stable package depends on package that were dropped of Debian, ergo Ubuntu 13.10:

libgd2 (2.0.36~rc1~dfsg-6.1) unstable; urgency=low

  * Non-maintainer upload.
  * Support multi-arch: (closes: #652496)
    - Mark libgd2-xpm, libgd2-noxpm, libgd2-xpm-dev and libgd2-noxpm-dev
      as same.
    - Adjust d-shlibs and dh-buildinfo build-dependency.
  * Drop .la files.

 -- Bastian Blank   Sun, 13 May 2012 09:16:37 +0000

Those are dependencies of graphviz so they should change them to libgd2-xpm-dev and libgd2-noxpm-dev respectively. If that's the case, you should download the latest build instead 2.38 or later, which includes the correct dependencies.