biber-2.6-6.fc28 fails to build in F28 because tests fail like this:

+ ./Build test
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 /builddir/build/BUILD/biber-2.6/blib/lib/Biber/LaTeX/Recode.pm line 297.
#   Failed test 'Annotations - 1'
#   at t/annotations.t line 87.
# --- Got
# +++ Expected
# @@ -1,39 +1,39 @@
#  '    \\entry{ann1}{misc}{}
#        \\name{author}{3}{}{%
#          {{hash=89a9e5097e11e595700540379c9b3a6b}{%
#             family={Last1},
#             familyi={L\\bibinitperiod},
#             given={First1},
#             giveni={F\\bibinitperiod}}}%
#          {{hash=7475b6b7b3c24a2ac6bd4d146cdc74dc}{%
#             family={Last2},
#             familyi={L\\bibinitperiod},
#             given={First2},
#             giveni={F\\bibinitperiod}}}%
#          {{hash=fd3dffa06a5d1f89c512841df1ccf4d0}{%
#             family={Last3},
#             familyi={L\\bibinitperiod},
#             given={First3},
#             giveni={F\\bibinitperiod}}}%
#        }
#        \\list{language}{2}{%
#          {english}%
#          {french}%
#        }
#        \\strng{namehash}{90ae96c82de92e36949bc64254bbde0c}
#        \\strng{fullhash}{90ae96c82de92e36949bc64254bbde0c}
#        \\strng{authornamehash}{90ae96c82de92e36949bc64254bbde0c}
#        \\strng{authorfullhash}{90ae96c82de92e36949bc64254bbde0c}
#        \\field{sortinit}{L}
# -      \\field{sortinithash}{2c7981aaabc885868aba60f0c09ee20f}
# +      \\field{sortinithash}{7bba64db83423e3c29ad597f3b682cf3}
#        \\field{labelnamesource}{author}
#        \\field{labeltitlesource}{title}
#        \\field{title}{The Title}
#        \\annotation{field}{language}{}{}{ann4}
#        \\annotation{field}{title}{}{}{one, two}
#        \\annotation{item}{author}{2}{}{corresponding}
#        \\annotation{item}{language}{1}{}{ann1}
#        \\annotation{item}{language}{2}{}{ann2, ann3}
#        \\annotation{part}{author}{1}{family}{student}
#      \\endentry
#  '
# Looks like you failed 1 test of 1.
t/annotations.t ........ 
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/1 subtests 

This is caused by upgrading perl-Unicode-Collate from 1.20-1.fc28 to 1.21-1.fc28. The biber tests are oversensitive to Unicode::Collate capabilities. Upstream fixed biber with this commit:

commit 33848fc870a7df93074bc938117d447a1d104f4b
Author: Philip Kime <Philip.uk>
Date:   Mon Nov 6 14:03:43 2017 +0100

    Update sortinithas for new U::C keys

I pushed perl-Unicode-Collate-1.21 into all Fedoras as an enhancement updated (not yet stable), so I guess this biber commit should be applied to all Fedoras too.