Error running pgadmin4 after installing package via apt

Hi,

I found there is a packaged version of pgadmin4 available for Debian OS: https://www.pgadmin.org/download/pgadmin-4-apt/

But I couldn't find any installation guide so what I tried was:

> apt-get install pgadmin4

It worked fine but when I run pgadmin4 it failed:

 > pgadmin4
Python path:  ""
Python Home:  ""
Webapp path:  "/usr/share/pgadmin4/web/pgAdmin4.py"
Traceback (most recent call last):
  File "/usr/share/pgadmin4/web/pgAdmin4.py", line 34, in <module>
    import config
  File "/usr/share/pgadmin4/web/config.py", line 30, in <module>
    from pgadmin.utils import env, IS_PY2, IS_WIN, fs_short_path
  File "/usr/share/pgadmin4/web/pgadmin/__init__.py", line 17, in <module>
    from flask import Flask, abort, request, current_app, session, url_for
ImportError: No module named 'flask'

Segmentation fault (core dumped)

I guess something is missing or some configuration is required but I couldn't find anything about it.

I tried to fix it by setting the PYTHONPATH property but it didn't work either (although the error changed):

> export PYTHONPATH=~/apps/pgadmin4/venv/lib/python2.7/site-packages/
> pgadmin4
Python path:  ""
Python Home:  ""
Webapp path:  "/usr/share/pgadmin4/web/pgAdmin4.py"
Traceback (most recent call last):
  File "/usr/share/pgadmin4/web/pgAdmin4.py", line 67, in <module>
    app = create_app()
  File "/usr/share/pgadmin4/web/pgadmin/__init__.py", line 357, in create_app
    driver.init_app(app)
  File "/usr/share/pgadmin4/web/pgadmin/utils/driver/__init__.py", line 40, in init_app
    DriverRegistry.load_drivers()
  File "/usr/share/pgadmin4/web/pgadmin/utils/driver/registry.py", line 88, in load_drivers
    module = import_module(module_name)
  File "/usr/lib/python3.5/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 986, in _gcd_import
  File "<frozen importlib._bootstrap>", line 969, in _find_and_load
  File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 673, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 665, in exec_module
  File "<frozen importlib._bootstrap>", line 222, in _call_with_frames_removed
  File "/usr/share/pgadmin4/web/pgadmin/utils/driver/psycopg2/__init__.py", line 23, in <module>
    import psycopg2
  File "/home/sabela/apps/pgadmin4/venv/lib/python2.7/site-packages/psycopg2/__init__.py", line 50, in <module>
    from psycopg2._psycopg import (                     # noqa
ImportError: /home/sabela/apps/pgadmin4/venv/lib/python2.7/site-packages/psycopg2/_psycopg.so: undefined symbol: PyUnicodeUCS4_DecodeUTF8

Segmentation fault (core dumped)

In both cases, a popup with the pgAdmin logo is shown and, after a while, a new popup with the message "The application server could not be contacted" appears.

Could you please help me to solve this or point me to the right resource?

Many thanks!