weasyprint fails in tests:

...
=================================== FAILURES ===================================
__________________________________ test_acid2 __________________________________

    @assert_no_logs
    @requires('cairo', (1, 12, 0))
    def test_acid2():
        def render(filename):
            return HTML(resource_filename(filename)).render(enable_hinting=True)
    
        with capture_logs():
            # This is a copy of http://www.webstandards.org/files/acid2/test.html
            document = render('acid2-test.html')
            intro_page, test_page = document.pages
            # Ignore the intro page: it is not in the reference
            test_image, width, height = document.copy(
                [test_page]).write_image_surface()
    
        # This is a copy of http://www.webstandards.org/files/acid2/reference.html
        ref_image, ref_width, ref_height = render(
            'acid2-reference.html').write_image_surface()
    
        assert (width, height) == (ref_width, ref_height)
>       assert_pixels_equal(
            'acid2', width, height, image_to_pixels(test_image, width, height),
            image_to_pixels(ref_image, width, height), tolerance=2)

weasyprint/tests/test_acid2.py:37: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

name = 'acid2', width = 794, height = 1123
raw = b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00...00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
expected_raw = b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00...00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
tolerance = 2

    def assert_pixels_equal(name, width, height, raw, expected_raw, tolerance=0):
        """Take 2 matrices of pixels and assert that they are the same."""
        if raw != expected_raw:  # pragma: no cover
            for i, (value, expected) in enumerate(zip(raw, expected_raw)):
                if abs(value - expected) > tolerance:
                    write_png(name, raw, width, height)
                    write_png(name + '.expected', expected_raw,
                              width, height)
                    pixel_n = i // 4
                    x = pixel_n // width
                    y = pixel_n % width
                    i % 4
                    pixel = tuple(list(raw[i:i + 4]))
                    expected_pixel = tuple(list(
                        expected_raw[i:i + 4]))
>                   assert 0, (
                        'Pixel (%i, %i) in %s: expected rgba%s, got rgba%s'
                        % (x, y, name, expected_pixel, pixel))
E                   AssertionError: Pixel (124, 160) in acid2: expected rgba(191, 127, 127, 255), got rgba(128, 0, 0, 255)

weasyprint/tests/test_draw/__init__.py:163: AssertionError
------------------------------ Captured log call -------------------------------
INFO     weasyprint.progress:__init__.py:106 Step 1 - Fetching and parsing HTML - /tmp/guix-build-weasyprint-51.drv-0/WeasyPrint-51/weasyprint/tests/resources/acid2-test.html
INFO     weasyprint.progress:__init__.py:315 Step 2 - Fetching and parsing CSS - CSS string
WARNING  weasyprint:__init__.py:825 Invalid or unsupported selector '[class=second two] ', (<IdentToken two>, 'expected ], got ident')
WARNING  weasyprint:__init__.py:86 Ignored `error: \}` at 90:74, unknown property.
WARNING  weasyprint:__init__.py:86 Ignored `m
rgin: 2em` at 93:14, unknown property.
WARNING  weasyprint:__init__.py:825 Invalid or unsupported selector ';
   .parser ', (<LiteralToken ;>, 'expected a compound selector, got literal')
WARNING  weasyprint:__init__.py:86 Ignored `width: 200` at 95:14, invalid value.
WARNING  weasyprint:__init__.py:86 Ignored `border: 5em solid red ! error` at 96:14, invalid value.
WARNING  weasyprint:__init__.py:86 Ignored `background: red pink` at 97:14, invalid value.
INFO     weasyprint.progress:__init__.py:315 Step 2 - Fetching and parsing CSS - data:text/css,.picture%20%7B%20background%3A%20none%3B%20%7D
INFO     weasyprint.progress:__init__.py:67 Step 3 - Applying CSS
INFO     weasyprint.progress:document.py:371 Step 4 - Creating formatting structure
ERROR    weasyprint:images.py:231 Failed to load image at "file:///tmp/guix-build-weasyprint-51.drv-0/WeasyPrint-51/weasyprint/tests/resources/404" (URLError: <urlopen error [Errno 2] No such file or directory: '/tmp/guix-build-weasyprint-51.drv-0/WeasyPrint-51/weasyprint/tests/resources/404'>)
ERROR    weasyprint:images.py:231 Failed to load image at "data:application/x-unknown,ERROR" (Pixbuf error: Unrecognized image file format)
INFO     weasyprint.progress:pages.py:798 Step 5 - Creating layout - Page 1
INFO     weasyprint.progress:pages.py:798 Step 5 - Creating layout - Page 2
INFO     weasyprint.progress:document.py:751 Step 6 - Drawing
INFO     weasyprint.progress:__init__.py:106 Step 1 - Fetching and parsing HTML - /tmp/guix-build-weasyprint-51.drv-0/WeasyPrint-51/weasyprint/tests/resources/acid2-reference.html
INFO     weasyprint.progress:__init__.py:315 Step 2 - Fetching and parsing CSS - CSS string
INFO     weasyprint.progress:__init__.py:67 Step 3 - Applying CSS
INFO     weasyprint.progress:document.py:371 Step 4 - Creating formatting structure
INFO     weasyprint.progress:pages.py:798 Step 5 - Creating layout - Page 1
INFO     weasyprint.progress:document.py:751 Step 6 - Drawing
______________________________ test_line_content _______________________________

    @assert_no_logs
    def test_line_content():
        for width, remaining in [(100, 'text for test'),
                                 (45, 'is a text for test')]:
            text = 'This is a text for test'
            _, length, resume_at, _, _, _ = make_text(
                text, width, font_family=SANS_FONTS.split(','), font_size=19)
>           assert text[resume_at:] == remaining
E           AssertionError: assert 'a text for test' == 'text for test'
E             - a text for test
E             ? --
E             + text for test

../../../WeasyPrint-51/weasyprint/tests/test_text.py:37: AssertionError
______________________________ test_line_breaking ______________________________

    @assert_no_logs
    def test_line_breaking():
        string = 'Thïs is a text for test'
    
        # These two tests do not really rely on installed fonts
        _, _, resume_at, _, _, _ = make_text(string, 90, font_size=1)
        assert resume_at is None
    
        _, _, resume_at, _, _, _ = make_text(string, 90, font_size=100)
        assert string.encode('utf-8')[resume_at:].decode('utf-8') == (
            'is a text for test')
    
        _, _, resume_at, _, _, _ = make_text(
            string, 100, font_family=SANS_FONTS.split(','), font_size=19)
>       assert string.encode('utf-8')[resume_at:].decode('utf-8') == (
            'text for test')
E       AssertionError: assert 'a text for test' == 'text for test'
E         - a text for test
E         ? --
E         + text for test

../../../WeasyPrint-51/weasyprint/tests/test_text.py:62: AssertionError

...

= 41 failed, 1132 passed, 1 deselected, 7 xfailed, 1 warning in 84.56s (0:01:24) =
command "pytest" "-k" "not test_flex_column_wrap_reverse" failed with status 1
builder for `/gnu/store/5c9h7c9pnrbpmk1015vrckrwsf5hd5xr-weasyprint-51.drv' failed with exit code 1


-- 
"We all know Linux is great...it does infinite loops in 5 seconds."
(Linus Torvalds about the superiority of Linux on the Amterdam
Linux Symposium)