Not able to lauch firefox using RobotFramework

Question

I am getting below error when i try to launch the firefox browser from robot framework script. Below is the error which i am getting. Can you please let me know how to resolve this issue. I have copied the geckodriver.exe under c:\python\scripts folder

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SessionNotCreatedException: Message: Expected browser binary location, but unable to find binary in default location, no 'moz:firefoxOptions.binary' capability provi
ded, and no binary flag set on the command line
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Robot script code:

*** Settings ***
Library  SeleniumLibrary
Library  ../PageObjects/Locators.py
Resource  ../Resources/loginKeywords.robot
#Resource  ../PageObjects/Locators.py
Suite Setup  Open my browser
Suite Teardown  close all browsers

*** Variables ***

#${url}  http://demo.guru99.com/test/newtours/
${username}  admin
${password}  admin
${browser}  firefox

*** Keywords ***

*** Test Cases ***
TestCase_001
  hello world
  Enter username  ${username}
  Enter Password  ${password}
  Click Submit
  sleep  5