Error cloning private submodule repo

00:13:34.656    Cloning repository...
00:13:35.299    From https://github.com/*************
00:13:35.300     * branch            7ecd7d19c93e16fc145f8323882c70c20d31c62b -> FETCH_HEAD
00:13:35.300    
00:13:35.328    HEAD is now at 7ecd7d1 add test-private to test private
00:13:35.328    
00:13:35.858    Submodule 'src/content/test-private' (https://github.com/**************) registered for path 'src/content/test-private'
00:13:35.858    Cloning into '/opt/buildhome/clone/src/content/test-private'...
00:13:35.858    fatal: could not read Username for 'https://github.com': Input/output error
00:13:35.859    fatal: clone of 'https://github.com/*****************' into submodule path '/opt/buildhome/clone/src/content/test-private' failed
00:13:35.859    Failed to clone 'src/content/test-private'. Retry scheduled
00:13:35.859    Cloning into '/opt/buildhome/clone/src/content/test-private'...
00:13:35.859    fatal: could not read Username for 'https://github.com': Input/output error
00:13:35.859    fatal: clone of 'https://github.com/**************' into submodule path '/opt/buildhome/clone/src/content/test-private' failed
00:13:35.859    Failed to clone 'src/content/test-private' a second time, aborting
00:13:35.859    
00:13:36.546    Failed: error occurred while updating repository submodules