diff: fix two-way diff for added or removed files Viewing the two-way diff of an added file gives following exception: File "_base_root_html", line 211, in render_body File "_base_base_html", line 42, in render_body File "files_diff_2way_html", line 197, in render_main File ".../kallithea/lib/vcs/nodes.py", line 411, in is_binary return b'\0' in self.content TypeError: 'in <string>' requires string as left operand, not bytes At this point, self.content was '' (empty string). Commit 9203621cae03a03bbf8cfb4b667daa656780a93e made that node content is always bytes, but this also had to be reflected in EmptyChangeset. Add a basic test that catches this behavior.

[pytest]
# only look for tests in kallithea/tests
python_files = kallithea/tests/**/test_*.py
addopts =
    # --verbose
    # show extra test summary info as specified by chars (f)ailed, (E)error, (s)skipped, (x)failed, (X)passed, (w)warnings.
    -rfEsxXw
    # Shorter scrollbacks; less stuff to scroll through
    --tb=short
    #
    --doctest-modules
    --doctest-ignore-import-errors