[DRE-maint] Bug#794262: FTBFS: 44 tests fail: token safe; atom safe; Mail::Message, Mail::Encoding, etc.

[Chris West (Faux)]

Source: ruby-mail
Version: 2.6.1+dfsg1-1
Severity: serious
Tags: sid
Justification: fails to build from source
User: reproducible-builds at lists.alioth.debian.org
Usertags: ftbfs

Dear Maintainer,

The package fails to build:

Failures:

  1) Utilities Module token safe checking should return true if a string is token safe
     Failure/Error: token_safe?('.abc').should be_true
       expected true to respond to `true?` or perhaps you meant `be true` or `be_truthy`
     # ./spec/mail/utilities_spec.rb:12:in `block (4 levels) in <top (required)>'

  2) Utilities Module token safe checking should return false if a string is token safe
     Failure/Error: token_safe?('?=abc').should be_false
       expected false to respond to `false?` or perhaps you meant `be false` or `be_falsey`
     # ./spec/mail/utilities_spec.rb:16:in `block (4 levels) in <top (required)>'

....

66 deprecation warnings total

Finished in 15.68 seconds (files took 4.1 seconds to load)
1507 examples, 44 failures, 6 pending

Full build log:
https://reproducible.debian.net/rb-pkg/unstable/amd64/ruby-mail.html

-- System Information:
Debian Release: stretch/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 3.19.0-23-generic (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)