I use Developer Guide > API Versions > API-Version-8 > Configure SuiteCRM instruction but i got error while calling api/oauth/access_token api

I use Developer Guide > API Versions > API-Version-8 > Configure SuiteCRM instruction but i got error while calling api/oauth/access_token api. Error is as follows
{
“errors”: [
{
“code”: 0,
“title”: "Key path “file://-----BEGIN PUBLIC KEY----- MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDrgiG3WjsECAk7kGiEYGOn8sUj sfhnu9rXI+LuH2VPcV5YK1Qu0wApWG7AK233lIouezZOLSpAomXlKKi//9AJmGZ5 X8Lgc6z9pCRp1kG8mTMO/dxrYMsIbLA2pFwYXFI/dPnwzqfRtXGUi+90hdyzXHZ0 Mq44sBTOvbF0vAR0nQIDAQAB -----END PUBLIC KEY----- " does not exist or is not readable”,
“status”: 400
},
{
“id”: “1”,
“links”: {
“about”: null
},
“status”: “200”,
“code”: 0,
“title”: “JSON API Error”,
“detail”: “JSON API Error occured.”,
“source”: {
“pointer”: null,
“parameter”: null
},
“meta”: {
“about”: “Exception”,
“class”: “LogicException”,
“code”: 0
}
}
],
“meta”: {
“suiteapi”: {
“major”: 8,
“minor”: 0,
“patch”: 0,
“stability”: “ALPHA”
}
},
“jsonapi”: {
“version”: “1.0”
}
}

any help is appreciated. Thank in advance