GET_ACCOUNTS permission and Google API's

Question

I'm using the Gmail API to send emails from an Android app.
Reading about GET_ACCOUNTS permission lead me to think it's no longer necessary but apparently, I was wrong.

I personally use Android 8 and everything is working just fine without the permission declared, however, running Android 7 raises an exception from the Google GMS Auth lib: (I know, the exception doesn't look related, it is the permission issue)

java.lang.IllegalArgumentException: the name must not be empty: null
    at android.accounts.Account.<init>(Account.java:48)
    at com.google.android.gms.auth.zzd.getToken(Unknown Source)
    at com.google.android.gms.auth.GoogleAuthUtil.getToken(Unknown Source)
    at com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential.getToken(GoogleAccountCredential.java:267)
    at com.google.api.client.googleapis.extensions.android.gms.auth.GoogleAccountCredential$RequestHandler.intercept(GoogleAccountCredential.java:292)
    at com.google.api.client.http.HttpRequest.execute(HttpRequest.java:868)
    at com.google.api.client.googleapis.media.MediaHttpUploader.executeCurrentRequestWithoutGZip(MediaHttpUploader.java:545)
    at com.google.api.client.googleapis.media.MediaHttpUploader.executeCurrentRequest(MediaHttpUploader.java:562)
    at com.google.api.client.googleapis.media.MediaHttpUploader.executeUploadInitiation(MediaHttpUploader.java:519)
    at com.google.api.client.googleapis.media.MediaHttpUploader.resumableUpload(MediaHttpUploader.java:384)
    at com.google.api.client.googleapis.media.MediaHttpUploader.upload(MediaHttpUploader.java:336)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:427)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.executeUnparsed(AbstractGoogleClientRequest.java:352)
    at com.google.api.client.googleapis.services.AbstractGoogleClientRequest.execute(AbstractGoogleClientRequest.java:469)

So I guess I still need to declare it and ask the user to grant it on Android 7, but in what other SDK versions?
It looks like Android 8 doesn't need the permission, but what about Android 6 downwards?
I've looked all over the Google API's doc's but didn't find anything related...