[DRE-maint] Bug#795035: ruby-fast-gettext: FTBFS: The message expectation for #<FastGettext::MoFile (class)>.new has already been invoked

[Chris West (Faux)]

Source: ruby-fast-gettext
Version: 0.9.0-1
Severity: serious
Justification: fails to build from source
Tags: sid stretch
User: reproducible-builds at lists.alioth.debian.org
Usertags: ftbfs
X-Debbugs-CC: reproducible-builds at lists.alioth.debian.org

Dear Maintainer,

The package fails to build:

┌──────────────────────────────────────────────────────────────────────────────┐
│ Run tests for ruby2.1 from debian/ruby-tests.rb                              │
└──────────────────────────────────────────────────────────────────────────────┘

RUBYLIB=/ruby-fast-gettext-0.9.0/debian/ruby-fast-gettext/usr/lib/ruby/vendor_ruby:. ruby2.1 debian/ruby-tests.rb
poparser.ry:244: warning: IO#lines is deprecated; use #each_line instead
............................................................................................poparser.ry:244: warning: IO#lines is deprecated; use #each_line instead
poparser.ry:244: warning: IO#lines is deprecated; use #each_line instead
poparser.ry:244: warning: IO#lines is deprecated; use #each_line instead
...
poparser.ry:244: warning: IO#lines is deprecated; use #each_line instead
poparser.ry:244: warning: IO#lines is deprecated; use #each_line instead
....................FF.....................................................................................

Failures:

  1) FastGettext::TranslationRepository::Mo reload can reload
     Failure/Error: FastGettext::MoFile.stub(:new).and_return(FastGettext::MoFile.empty)
       The message expectation for #<FastGettext::MoFile (class)>.new has already been invoked and cannot be modified further (e.g. using `and_return`). All message expectation customizations must be applied before it is used for the first time.
     # ./spec/fast_gettext/translation_repository/mo_spec.rb:27:in `block (3 levels) in <top (required)>'

  2) FastGettext::TranslationRepository::Mo reload returns true
     Failure/Error: FastGettext::MoFile.stub(:new).and_return(FastGettext::MoFile.empty)
       The message expectation for #<FastGettext::MoFile (class)>.new has already been invoked and cannot be modified further (e.g. using `and_return`). All message expectation customizations must be applied before it is used for the first time.
     # ./spec/fast_gettext/translation_repository/mo_spec.rb:27:in `block (3 levels) in <top (required)>'

Full build log:
https://reproducible.debian.net/rb-pkg/unstable/amd64/ruby-fast-gettext.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_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)