Run Black formatter

When there is a large diff chunk, match_lines() will skip running the
difflib.Differ.compare(). However this causes the following issues:

- It does not empty the `self.buf` buffer. This means that all future
  calls to match_lines() for that file will always be too large. So
  effectively no more diffs from the file get output.

- It outputs a debug message, but does not output anything to the
  side-by-side diff, so a user looking at the side-by-side diff may be
  misled into thinking the rest of the file has no differences.

We can fix these issue by falling back to a lazy line-by-line diff. This
produces suboptimal output, but it runs in linear O(n) time while
providing some form of output. We include a comment in the diff so the
user knows the following output is using a lazy diff algorithm.

Continue loading a .changes file if the referenced files do not exist, but include a comment in the returned diff.

Don't reject Debian .changes files if they contain non-printable characters. (Closes: reproducible-builds/diffoscope#286)

With this change, tests actually pass with python 3.10
(python3-3.10.0-1.fc35.x86_64).

Gbp-Dch: ignore

Gbp-Dch: Ignore
Signed-off-by: Mattia Rizzolo <mattia@debian.org>

Don't raise a traceback if we cannot de-marshal Python bytecode to support Python 3.7 loading newer .pyc files. (Re: reproducible-builds/diffoscope#284)

(Closes: reproducible-builds/diffoscope#284)

Revert "Skip Python bytecode testing where we do not have an expected diff. (Closes: reproducible-builds/diffoscope#284)"

This reverts commit ef878eca.

Gbp-Dch: ignore

Skip Python bytecode testing where we do not have an expected diff. (Closes: reproducible-builds/diffoscope#284)

This still ignores one unit test set which fails on Arch Linux and
needs to be further investigated.

File-5.40->5.41 upgrade brought uImage printing change
which removed 0x prefixes in a few places:
  https://github.com/file/file/commit/905ca555b0e2bdcf9d2985bcc7c1c22e2229b088

This caused test faiure:
  E       AssertionError: assert '@@ -1 +1 @@\... 0XC63C4A06\n' == '@@ -1 +1 @@\... 0xC63C4A06\n'
  E         Skipping 127 identical leading characters in diff, use -v to show
  E         - Address: 0x00000000, Entry Point: 0x00000000, Header CRC: 0xF87AD200, Data CRC: 0x347161A5
  E         ?          --                       --                       ^                     ^
  E         + Address: 00000000, Entry Point: 00000000, Header CRC: 0XF87AD200, Data CRC: 0X347161A5
  E         ?                                                        ^                     ^

The change adds new variant of expected output.

Try some alternative suffixes (eg. ".py") to support distributions that strip or retain them. (Closes: reproducible-builds/diffoscope#283)

Strictly speaking, the package in Guiux ships dumppdf.py, but this
should reduce the downstream diff.

Gbp-Dch: ignore

Gbp-Dch: ignore

Gbp-Dch: Ignore
Signed-off-by: Mattia Rizzolo <mattia@debian.org>

Add support for comparing .pyc files. Thanks to Sergei Trofimovich. (Closes: reproducible-builds/diffoscope#278)

Gbp-Dch: ignore