Startup problem pgadmin4 V1.2 on osx 10.10.5 Yosemite

Hi,

i updated pgadmin4 from v1.1 to v1.2.

after starting the v1.2 app, a small blue pgadmin banner appears (pgadmin Management tool),
when this vanished, a somewhat bigger window opens and displays an error message:

the website is not available
ERR_CONNECTION_REFUSED

a bit later an another error message appears:
Failed to connect to the pgAdmin application server. Click here to try again.

clicking the link, displays the same error message again.

pgadmin4 V1.1 works, pgadmin4 V1.2 does not starts

Working version:
Version1.1
CopyrightCopyright 2013 - 2016, The pgAdmin Development Team
Python Version2.7.10 (default, Jul 14 2015, 19:46:27) [GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)]
Flask Version0.11.1

Failing version:
1.2
downloaded at 2017-03-10 10:00 CET

content of ~/.pgadmin/pgadmin4.log:
2017-03-10 10:07:37,900: INFO pgadmin: ########################################################
2017-03-10 10:07:37,900: INFO pgadmin: Starting pgAdmin 4 v1.2...
2017-03-10 10:07:37,900: INFO pgadmin: ########################################################
2017-03-10 10:08:30,957: INFO pgadmin: ########################################################
2017-03-10 10:08:30,957: INFO pgadmin: Starting pgAdmin 4 v1.2...
2017-03-10 10:08:30,958: INFO pgadmin: ########################################################

deleting the folder ~/.pgadmin did not helped
deleting ~/Library/Application Support/pgadmin not helped

ist there a solution to this problem?

thanks

Attila