title: Problems instaling libpq-dev in ubuntu 20.04
body: <p>I am currently trying to install libpq-dev to install psycopg2. The problem is, when I try to install it, an error occurs saying I don't have the latest libpq5 version. However when I try to download the newer version of libpq5 the system says that I already have the latest version. An example of the error.</p>
  <pre><code>lhmendes@lhmendes-GA-78LMT-S2P:~$ sudo apt-get install libpq-dev
  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:
   libpq-dev : Depends: libpq5 (= 12.4-0ubuntu0.20.04.1) but 12.4-1.pgdg20.04+1 is to be installed
  E: Unable to correct problems, you have held broken packages.
  lhmendes@lhmendes-GA-78LMT-S2P:~$ sudo apt-get install libpq5
  Reading package lists... Done
  Building dependency tree       
  Reading state information... Done
  libpq5 is already the newest version (12.4-1.pgdg20.04+1).
  0 upgraded, 0 newly installed, 0 to remove and 4 not upgraded.
  </code></pre>