Meta -

OS: Mac OS El Capitan 10.11.6

Selenium Version: 3.3.3

Browser: Firefox

Browser Version: 52.0.2 (64-bit)

Expected Behavior -

In python, the following should create a Remote driver:

from selenium import webdriver

cap = {'platform': 'ANY', 'browserName': 'firefox', 'version': '', 'marionette': True, 'javascriptEnabled': True}
driver = webdriver.Remote(command_executor='http://<my_server_ip>:4444/wd/hub', desired_capabilities=cap)

(note: this works with selenium 2.53.6 with python2.7 when executed against the same server)

Actual Behavior -

Thows exception: KeyError: 'message'

When I pdb into this I see the following response from the server:

{'value': '{"status":13,"value":{"class":"java.lang.NullPointerException","stackTrace":[{"fileName":"HashMap.java","className":"java.util.HashMap","methodName":"putMapEntries","lineNumber":500},{"fileName":"HashMap.java","className":"java.util.HashMap","methodName":"putAll","lineNumber":784},{"fileName":"DesiredCapabilities.java","className":"org.openqa.selenium.remote.DesiredCapabilities","methodName":"\u003cinit\u003e","lineNumber":54},{"fileName":"RequestHandler.java","className":"org.openqa.grid.web.servlet.handler.RequestHandler","methodName":"process","lineNumber":104},{"fileName":"DriverServlet.java","className":"org.openqa.grid.web.servlet.DriverServlet","methodName":"process","lineNumber":83},{"fileName":"DriverServlet.java","className":"org.openqa.grid.web.servlet.DriverServlet","methodName":"doPost","lineNumber":67},{"fileName":"HttpServlet.java","className":"javax.servlet.http.HttpServlet","methodName":"service","lineNumber":707},{"fileName":"HttpServlet.java","className":"javax.servlet.http.HttpServlet","methodName":"service","lineNumber":790},{"fileName":"ServletHolder.java","className":"org.seleniumhq.jetty9.servlet.ServletHolder","methodName":"handle","lineNumber":841},{"fileName":"ServletHandler.java","className":"org.seleniumhq.jetty9.servlet.ServletHandler","methodName":"doHandle","lineNumber":543},{"fileName":"ScopedHandler.java","className":"org.seleniumhq.jetty9.server.handler.ScopedHandler","methodName":"nextHandle","lineNumber":188},{"fileName":"SessionHandler.java","className":"org.seleniumhq.jetty9.server.session.SessionHandler","methodName":"doHandle","lineNumber":1584},{"fileName":"ScopedHandler.java","className":"org.seleniumhq.jetty9.server.handler.ScopedHandler","methodName":"nextHandle","lineNumber":188},{"fileName":"ContextHandler.java","className":"org.seleniumhq.jetty9.server.handler.ContextHandler","methodName":"doHandle","lineNumber":1228},{"fileName":"ScopedHandler.java","className":"org.seleniumhq.jetty9.server.handler.ScopedHandler","methodName":"nextScope","lineNumber":168},{"fileName":"ServletHandler.java","className":"org.seleniumhq.jetty9.servlet.ServletHandler","methodName":"doScope","lineNumber":481},{"fileName":"SessionHandler.java","className":"org.seleniumhq.jetty9.server.session.SessionHandler","methodName":"doScope","lineNumber":1553},{"fileName":"ScopedHandler.java","className":"org.seleniumhq.jetty9.server.handler.ScopedHandler","methodName":"nextScope","lineNumber":166},{"fileName":"ContextHandler.java","className":"org.seleniumhq.jetty9.server.handler.ContextHandler","methodName":"doScope","lineNumber":1130},{"fileName":"ScopedHandler.java","className":"org.seleniumhq.jetty9.server.handler.ScopedHandler","methodName":"handle","lineNumber":141},{"fileName":"HandlerWrapper.java","className":"org.seleniumhq.jetty9.server.handler.HandlerWrapper","methodName":"handle","lineNumber":132},{"fileName":"Server.java","className":"org.seleniumhq.jetty9.server.Server","methodName":"handle","lineNumber":564},{"fileName":"HttpChannel.java","className":"org.seleniumhq.jetty9.server.HttpChannel","methodName":"handle","lineNumber":320},{"fileName":"HttpConnection.java","className":"org.seleniumhq.jetty9.server.HttpConnection","methodName":"onFillable","lineNumber":251},{"fileName":"AbstractConnection.java","className":"org.seleniumhq.jetty9.io.AbstractConnection$ReadCallback","methodName":"succeeded","lineNumber":279},{"fileName":"FillInterest.java","className":"org.seleniumhq.jetty9.io.FillInterest","methodName":"fillable","lineNumber":112},{"fileName":"ChannelEndPoint.java","className":"org.seleniumhq.jetty9.io.ChannelEndPoint$2","methodName":"run","lineNumber":124},{"fileName":"QueuedThreadPool.java","className":"org.seleniumhq.jetty9.util.thread.QueuedThreadPool","methodName":"runJob","lineNumber":672},{"fileName":"QueuedThreadPool.java","className":"org.seleniumhq.jetty9.util.thread.QueuedThreadPool$2","methodName":"run","lineNumber":590},{"fileName":"Thread.java","className":"java.lang.Thread","methodName":"run","lineNumber":745}]}}', 'status': 500}

Steps to reproduce -

Execute the above steps in python using selenium 3.3.3, firefox 52.0.2, geckodriver 0.15.0. The server is using selenium-server-standalone-3.3.1.jar on ubuntu 16.10. I'm happy to provide the ip of the server privately if it'll help.