apt - broken packages with PgAdmin3 version 1.20 in Ubuntu 14 LTS

My pgadmin3 was perfect, working with PostgreSQL 9.3 (pg9.3)... Them I upgraded to pg9.4... And start the problems... Old pgAdmin3 not runs with new pg9.4, so pgAdmin3 needs also upgrade.

With pg9.4 working (perfect) I checked apt-cache policy pgadmin3 and see that candidate 1.20 was there, so I remove old pgadmin3 and install new pgadmin3... PROBLEM:

The following packages have unmet dependencies:
 pgadmin3 : Depends: libstdc++6 (>= 4.9) but ...
            Depends: ....
E: Unable to correct problems, you have held broken packages.

So, what I can do now?

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NOTES

Complete step-by-step and messagens,

1. All was working and I check,

   
   

   apt-cache policy pgadmin3
   pgadmin3:
     Installed: 1.18.1-2
     Candidate: 1.20.0-1.pgdg14.10+1
     Version table:
      1.20.0-1.pgdg14.10+1 0
        500 http://apt.postgresql.org/pub/repos/apt/ utopic-pgdg/main amd64 Packages
      *** 1.18.1-2 0
        500 http://br.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
        100 /var/lib/dpkg/status
   




2. The sudo apt-get remove pgadmin3 was ok. Now the check changes, apt-cache policy pgadmin3

   
   

   
   pgadmin3:
    Installed: (none)
    Candidate: 1.20.0-1.pgdg14.10+1
    Version table:
      1.20.0-1.pgdg14.10+1 0
        500 http://apt.postgresql.org/pub/repos/apt/ utopic-pgdg/main amd64 Packages
      1.18.1-2 0
        500 http://br.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages
        100 /var/lib/dpkg/status
   




3. The bug arrives here, after sudo apt-get update (ok), I do

   
   

   sudo apt-get install pgadmin3`
   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:
    pgadmin3 : Depends: libstdc++6 (>= 4.9) but 4.8.4-2ubuntu1~14.04 is to be installed
               Depends: libwxbase3.0-0 (>= 3.0.1) but it is not going to be installed
               Depends: libwxgtk3.0-0 (>= 3.0.1) but it is not going to be installed
   E: Unable to correct problems, you have held broken packages.
   

PS: the question How to install PgAdmin3 version 1.20.0 in Ubuntu 14.04 is about the same subject, but is poluted and not solve 2016's problems.

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This link says

There isn’t yet an apt-get package for pgAdmin 1.20.0. Step four above installs pgAdmin 1.18.0 which works with Postgres 9.4 but doesn’t provide 9.4-specific features. If you want to install pgAdmin 1.20.0 you currently need to install it from source.

But even its "(Update: on 6 January, Ubuntu’s automatic software updates upgraded pgAdmin to 1.20.0.)" is wrong, because apt-get not works as I showed.

pgadmin3 (= 1.20.0-1.pgdg14.10+1) needs libstdc++6 (>= 4.9) and this package isn't available for Trusty and as you say in your comments

I need Ubuntu LTS, LST, stable (!)

don't add a PPA with higher versions of libstdc++6. These packages are an integral part of the system.

Install pgadmin3 (= 1.18.1-2) again

sudo apt-get install pgadmin3=1.18.1-2

and wait some days for Ubuntu 16.04, the next LTS release.