Licence_check doesn't support symbolic links?

I'm building a new Python image on top of the `gcr.io/gcp-runtimes/ubuntu_16_0_4` base, and I get these errors from licence_check:

```
Step #4:      licenses.go:70: libssl-dev
Step #4:      licenses.go:46: Error reading license file for /usr/share/doc/libssl-dev/copyright: API error (404): {"message":"Could not find the file ../libssl1.0.0/copyright in container f901a2834bcdbb685f7b2887e48680445b0bbb0008d8441955ed2f3764d4a350"}

Step #4:      licenses.go:70: openssl
Step #4:      licenses.go:46: Error reading license file for /usr/share/doc/openssl/copyright: API error (404): {"message":"Could not find the file ../libssl1.0.0/copyright in container 3678efba6b806b7817848917bfcfbf8334b74477d4bff5e99cbc91c8a5fe341b"}
```

The noteworthy thing is that these seem to be the only license files that are symbolic links instead of regular files.

```shell
$ docker run -it my_container /bin/bash -c 'ls -l /usr/share/doc/*/copyright | grep -- "->"'
lrwxrwxrwx 1 root root 24 Dec 7 21:09 /usr/share/doc/libssl-dev/copyright -> ../libssl1.0.0/copyright
lrwxrwxrwx 1 root root 24 Jan 1 1970 /usr/share/doc/openssl/copyright -> ../libssl1.0.0/copyright
```