bug#29021: gnu: biber@2.7: "check" phase fails at "dateformats.t" tests

[Adonay Felipe Nogueira <adfeno@hyperbola.info>]

When attempting:

$ guix package --fallback -i biber

This is the interesting part of the output:

--8<---------------cut here---------------start------------->8---
starting phase `configure'
running `perl' with arguments ("Build.PL"
"--prefix=/gnu/store/0mkxal471rqb55zvnqrapp970irzdb5i-biber-2.7"
"--installdirs=site")
WARNING: the following files are missing in your kit:
        META.json
                META.yml
                Please inform the author.

Created MYMETA.yml and MYMETA.json
Creating new 'Build' script for 'biblatex-biber' version '2.7'
phase `configure' succeeded after 0.6 seconds
starting phase `patch-generated-file-shebangs'
phase `patch-generated-file-shebangs' succeeded after 0.0 seconds
starting phase `build'
Building biblatex-biber
phase `build' succeeded after 0.7 seconds
starting phase `check'
--8<---------------cut here---------------end--------------->8---

--8<---------------cut here---------------start------------->8---
t/crossrefs.t .......... ok
Unescaped left brace in regex is deprecated here (and will be fatal in
Perl 5.30
), passed through in regex; marked by <-- HERE in m/}(\pM+\pL){ <-- HERE
(?!\pL+
\\)/ at
/tmp/guix-build-biber-2.7.drv-0/biber-2.7/blib/lib/Biber/LaTeX/Recode.pm
line 316.

#   Failed test 'Extended years - 1'
#   at t/dateformats.t line 684.
# --- Got
# +++ Expected
# @@ -1 +1 @@
# --638829
# +17000002

#   Failed test 'Extended years - 2'
#   at t/dateformats.t line 685.
# --- Got
# +++ Expected
# @@ -1 +1 @@
# --5240781
# +-17000002
# Looks like you failed 2 tests of 45.
t/dateformats.t ........
Dubious, test returned 2 (wstat 512, 0x200)
Failed 2/45 subtests
--8<---------------cut here---------------end--------------->8---

--8<---------------cut here---------------start------------->8---
Test Summary Report
-------------------
t/dateformats.t      (Wstat: 512 Tests: 45 Failed: 2)
  Failed tests:  43-44
  Non-zero exit status: 2
Files=43, Tests=1061, 78 wallclock secs ( 0.64 usr  0.14 sys + 59.30
cusr 16.42 csys = 76.50 CPU)
Result: FAIL
Failed 1/43 test programs. 2/1061 subtests failed.
phase `check' failed after 79.2 seconds
builder for
`/gnu/store/07p6wbr4j2j3qy4151z0gak2dylwhrkm-biber-2.7.drv' failed
with exit code 1
guix package: error: build failed: build of
`/gnu/store/07p6wbr4j2j3qy4151z0gak2dylwhrkm-biber-2.7.drv' failed
--8<---------------cut here---------------end--------------->8---

The other parts are related to unescaped left braces, because Perl now
changed how the regular expressions work in the language of the same
name.

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