join() argument must be str or bytes, not 'NoneType' when run Open Eyes|lib='Selenium2Library'|tolerance=5

[nixuewei]

Describe the bug
join() argument must be str or bytes, not 'NoneType' when run Open Eyes|lib='Selenium2Library'|tolerance=5

To Reproduce
Steps to reproduce the behavior:

1. install pip install robotframework-eyes
2. install Imagemagick7 on windows10 or macos Catalina 10.15.5
3. copy code
   `*** Settings ***
   Test Teardown
   Library SeleniumLibrary
   Library RobotEyes

*** Test Cases ***
Sample visual regression test case
# Name of the example test case
Open Browser https://www.baidu.com/ chrome
Maximize Browser Window
Open Eyes lib='Selenium2Library' tolerance=5
Wait Until Element Is Visible id=kw
Capture Full Screen
Compare Images
Close Browser`
4. See error

Expected behavior
run successfully

Screenshots
Starting test: CBTCTest.Visual Regression.Sample visual regression test case
20200728 12:04:23.045 : INFO : Opening browser 'chrome' to base url 'https://www.baidu.com/'.
20200728 12:04:33.229 : FAIL : TypeError: join() argument must be str or bytes, not 'NoneType'
Ending test: CBTCTest.Visual Regression.Sample visual regression test case

Desktop (please complete the following information):

• OS: windows10 or macos Catalina 10.15.5
• Browser [chrome]

[jessezach]

@nixuewei Did you pass the path to baseline directory and output directory when running tests. Refer the ReadMe for the command.

[nixuewei]

sorry for my misunderstanding the document, after running on command, it works well. so great. thank you! please close it

[jessezach]

@nixuewei That's alright. I will add a validation for the path in the upcoming release to avoid any confusion. Keeping this ticket open until then.

[nixuewei]

that was great!