This problem is seen using lighty.io 14.0 and 15.1, but also seen with OpenDayLight Silicon and Phosphorus SR1 releases as well. 

Certain Broadband Forum Yang files cause the swagger in ODL to error. Specifically, one creates a device which contains the YANG file bbf-software-management, the device will get connected and mounted. However, the swagger will not allow access to the device, it will display a box with the following error:

Fetch error

Server Error http://10.184.144.176:8181/apidoc/openapi3/18/apis/mounts/5

It can be recreated by simply starting ODL and adding a device (netconf testtool) which contains yang file from the Broadband forum called "bbf-software-management@21-09-17.yang"file.  There are several yang files included in this JIRA.. a netconf test tool can be created using these files to reproduce the problem. 

The problem seems to be related to a "leaf" ref. The bbf-software-manager yang is an augmentation to ietf-hardware. Inside the model, it has the following for example:

choice selection-criteria {
    description
    "Selects the criteria to identify which
    entry in the list 'revision' should
    be replaced.";
    case id {
        description
         "This case specifies that the action
        is to replace the entry within the
        list 'revision' with the specified
        'id'. The entry must be neither
        active nor committed.";
        leaf id {
            type leafref

Unknown macro: {                path "../../../../../../../bbf-swm}

        must "../../../../../../../bbf-swm:revisions/bbf-swm:revision[bbf-          
      ....

 The leaf "id" here is a leafref. ODL cannot decipher this path - or fails to do so. Directly after this there is also an "alias leaf with the same issue. The paths for these seem to be correct.  A work around for this is to change the BBF yang to use the define that the path refers to .. that fixes the issue. 

For example doing this instead... 

leaf id {
     type uint8;

....