Mike Fleetwood authored Mar 11, 2018 and Curtis Gedak committed Mar 26, 2018

Found that older but still supported distributions Debian 8 and
Ubuntu 14.04 LTS don't have directory /dev/disk/by-path/.  This is used
by the BlockSpecial unit test as a source of a symbolic link to a block
special device.

This causes the unit test to fail like this:

    $ cd tests
    $ ./test_BlockSpecial
    ...
    [ RUN      ] BlockSpecialTest.NamedBlockSpecialObjectBySymlinkMatches
    test_BlockSpecial.cc:137: Failure
    Failed
    get_link_name(): Failed to open directory '/dev/disk/by-path'
    test_BlockSpecial.cc:168: Failure
    Failed
    follow_link_name(): Failed to resolve symbolic link ''
    test_BlockSpecial.cc:255: Failure
    Expected: (lnk.m_name.c_str()) != (bs.m_name.c_str()), actual: "" vs ""
    [  FAILED  ] BlockSpecialTest.NamedBlockSpecialObjectBySymlinkMatches (0 ms)
    ...
    [  FAILED  ] 1 test, listed below:
    [  FAILED  ] BlockSpecialTest.NamedBlockSpecialObjectBySymlinkMatches

     1 FAILED TEST

Which in turn causes make check and make distcheck to fail.

Use directory /dev/disk/by-id/ instead as it always exists.