Catch 'clipboard already open' errors in editors

Apparently following commits have not fixed the problem completely,
because it still happens (although not so often).

changeset: 2019:b8f795bdfe9f
user: Andrey Skvortsov <andrej.skvortzov@gmail.com>
date: Fri May 25 17:40:29 2018 +0300
summary: fix hangs on mouse selection in case if wxPython uses wxWidgets with GTK3+ support

changeset: 2018:5ce6d08ff2c7
user: Andrey Skvortsov <andrej.skvortzov@gmail.com>
date: Fri May 25 17:23:15 2018 +0300
summary: make clipboard open minimal time as wxPython documentation recommends

          <xsd:attribute name="Command" type="xsd:string" use="optional" default="make -C %(buildpath)s all BEREMIZSRC=%(src)s BEREMIZCFLAGS=%(cflags)s MD5=%(md5)s USE_BEREMIZ=1 FROM_BEREMIZ=1"/>