MongoError: E11000 duplicate key error collection: vpdb-production.users index: username_1 dup key: { : "idrospeed" }

[freezy]

View details in Rollbar: https://rollbar.com/freezy/server/items/54/

MongoError: E11000 duplicate key error collection: vpdb-production.users index: username_1 dup key: { : "idrospeed" }
  File "/var/www/server/production/v2.3.8/node_modules/mongoose/node_modules/mongodb/lib/core/error.js", line 44, in Function.create
        return new MongoError(options);
  File "/var/www/server/production/v2.3.8/node_modules/mongoose/node_modules/mongodb/lib/utils.js", line 150, in toError
      var e = MongoError.create({ message: msg, driver: true });
  File "/var/www/server/production/v2.3.8/node_modules/mongoose/node_modules/mongodb/lib/operations/common_functions.js", line 266, in coll.s.topology.insert
          return handleCallback(callback, toError(result.result.writeErrors[0]));
  File "/var/www/server/production/v2.3.8/node_modules/mongoose/node_modules/mongodb/lib/core/connection/pool.js", line 892, in operation.cb
          if (typeof cb === 'function') cb(err, reply);
  File "/var/www/server/production/v2.3.8/node_modules/mongoose/node_modules/mongodb/lib/core/connection/pool.js", line 408, in <unknown>
              return cb(err, result);
  File "internal/process/next_tick.js", line 132, in _combinedTickCallback
  File "internal/process/next_tick.js", line 181, in process._tickCallback