OpenType fonts with TrueType outlines (*.ttf) shouldn't generate a WARNING

WARNING (CSS-007) at "Dummy_EPUB3.epub/OEBPS/stylesheet.css" (line 18, col 71):
   Font-face reference OEBPS/fonts/PT-Sans-Italic.ttf refers to non-standard font type application/x-font-ttf.

This WARNING is not true.
The PT-Sans-Italic.ttf is an OpenType font with TrueType outlines which should be perfectly valid.
However, it's declared as application/x-font-ttf in the content.opf file which may seem wrong, but it's still the correct mime-type for OpenType with TrueType outlines.

Also, epubcheck seems to ignore the format() property of the @font-face declaration:

@font-face{
    font-family: 'PT-Sans';
    font-style: italic;
    font-weight: normal;
    src: url("fonts/PT-Sans-Italic.ttf") format('opentype');
}

Seems as epubcheck only checks the file extension and throws a warning for *.ttf in general instead of checking the format() property and then examining the font file itself.