cert generated by tuto cannot be imported to azure keyvault

Hello,

I followed the [tuto](https://github.com/Azure-Samples/ms-identity-python-daemon/blob/master/2-Call-MsGraph-WithCertificate/README.md#optional-create-a-self-signed-certificate) in this repo to create the cert: `server.pem`, `server.crt`.
Uploading `server.crt` to app's `Certificates & secrets` as described in the tuto is OK, and the API test is OK too.

But when I tried to upload the cert to Azure Keyvault, `server.crt` is not validated as Azure keyvault accepts pem file only, but when uploading `server.pem` to Azure keyvault, I got the error: `The specified PEM X.509 certificate content can not be read. Please check if certificate is in valid PEM format. Accepted formats: PEM content or Base64 encoded PEM content.`