Comparisons of basic_string_views with custom char_traits do not print out the string values

[Marc-Aldorasi-Imprivata]

When I run the following tests

struct custom_char_traits : std::char_traits<char> {};

BOOST_AUTO_TEST_CASE(custom_char_traits_compare)
{
    using sv = std::basic_string_view<char, custom_char_traits>;
    sv sv1 = "sv1";
    sv sv2 = "sv2";
    BOOST_TEST(sv1 == sv2);
}

BOOST_AUTO_TEST_CASE(std_char_traits_compare)
{
    using sv = std::basic_string_view<char, std::char_traits<char>>;
    sv sv1 = "sv1";
    sv sv2 = "sv2";
    BOOST_TEST(sv1 == sv2);
}

I get the following output

*** 2 failures are detected in the test module "string view comparison"
Running 2 test cases...
example.cpp(14): error: in "custom_char_traits_compare": check sv1 == sv2 has failed
example.cpp(22): error: in "std_char_traits_compare": check sv1 == sv2 has failed [sv1 != sv2]

The error message for std_char_traits_compare contains the string values, but the error for custom_char_traits_compare does not.
Boost Test should display the compared strings regardless of what traits they have.