Update: after leaving my laptop and back again several minutes, the error message is gone and I see the main dashboard.
Looking to the console, there was a 15 minutes gap, then I saw some errors on the console:
16:19:22 web.1 | * Restarting with inotify reloader
16:19:23 web.1 | * Debugger is active!
16:19:23 web.1 | * Debugger PIN: 302-015-712
--- idle ---
16:34:42 web.1 | 127.0.0.1 - - [31/May/2018 16:34:42] "POST / HTTP/1.1" 200 -
16:34:45 web.1 | 127.0.0.1 - - [31/May/2018 16:34:45] "GET /robots.txt HTTP/1.1" 200 -
16:34:46 web.1 | 127.0.0.1 - - [31/May/2018 16:34:46] "GET /api/method/frappe.async.get_user_info?sid=2d7227b05c9a7a4ed19354dfe1a53d6369e60a8088c08c1d8f3bb927 HTTP/1.1" 200 -
16:34:54 web.1 | 127.0.0.1 - - [31/May/2018 16:34:54] "GET /desk HTTP/1.1" 200 -
16:34:54 web.1 | 127.0.0.1 - - [31/May/2018 16:34:54] "GET /assets/js/control.min.js?ver=1527773796.0 HTTP/1.1" 200 -
16:34:54 web.1 | 127.0.0.1 - - [31/May/2018 16:34:54] "GET /assets/js/report.min.js?ver=1527773796.0 HTTP/1.1" 200 -
16:34:54 web.1 | Error on request:
16:34:54 web.1 | Traceback (most recent call last):
16:34:54 web.1 | File "/home/yyy/frappe-bench/env/lib/python2.7/site-packages/werkzeug/serving.py", line 270, in run_wsgi
16:34:54 web.1 | execute(self.server.app)
16:34:54 web.1 | File "/home/yyy/frappe-bench/env/lib/python2.7/site-packages/werkzeug/serving.py", line 261, in execute
16:34:54 web.1 | write(data)
16:34:54 web.1 | File "/home/yyy/frappe-bench/env/lib/python2.7/site-packages/werkzeug/serving.py", line 227, in write
16:34:54 web.1 | self.send_header(key, value)
16:34:54 web.1 | File "/usr/lib/python2.7/BaseHTTPServer.py", line 412, in send_header
16:34:54 web.1 | self.wfile.write("%s: %s\r\n" % (keyword, value))
16:34:54 web.1 | IOError: [Errno 32] Broken pipe
...
16:34:57 web.1 | ----------------------------------------
16:34:57 web.1 | Exception happened during processing of request from ('127.0.0.1', 37792)
16:34:57 web.1 | Unhandled exception in thread started by <bound method Thread.__bootstrap of <Thread(Thread-31, stopped daemon 139775498512128)>>
16:34:57 web.1 | Traceback (most recent call last):
16:34:57 web.1 | File "/usr/lib/python2.7/threading.py", line 774, in __bootstrap
16:34:57 web.1 | ----------------------------------------
16:34:57 web.1 | Exception happened during processing of request from ('127.0.0.1', 37762)
16:34:57 web.1 | Unhandled exception in thread started by <bound method Thread.__bootstrap of <Thread(Thread-28, stopped daemon 139776036411136)>>
16:34:57 web.1 | Traceback (most recent call last):
16:34:57 web.1 | File "/usr/lib/python2.7/threading.py", line 774, in __bootstrap
16:34:57 web.1 | self.__bootstrap_inner()
16:34:57 web.1 | File "/usr/lib/python2.7/threading.py", line 814, in __bootstrap_inner
16:34:57 web.1 | (self.name, _format_exc()))
16:34:57 web.1 | File "/usr/lib/python2.7/traceback.py", line 241, in format_exc
16:34:57 web.1 | etype, value, tb = sys.exc_info()
16:34:57 web.1 | AttributeError: 'NoneType' object has no attribute 'exc_info'