This article was contributed by @kwoylie, and applies if you have a Gemfile in your repository and you use the fastlane step which uses the Gemfile automatically if present.

Issue:

Gemfile content was:

gem "fastlane", "1.104.0" 
gem "gym", "1.10.0" 
gem "badge", "0.5.0" 
gem "CFPropertyList","2.3.3" 
gem "sqlite3", "1.3.11"

Fastlane, with xcpretty disabled, produced the following error on Bitrise:

$/usr/bin/xcrun /usr/local/lib/ruby/gems/2.3.0/gems/gym-1.10.0/lib/assets/wrap_xcodebuild/xcbuild-safe.sh -exportArchive -exportOptionsPlist '/var/folders/90/5stft2v13fb_m_gv3c8x9nwc0000gn/T/gym_config20161003-2206-1f0vw3k.plist' -archivePath /Users/vagrant/Library/Developer/Xcode/Archives/2016-10-03/App\ 2016-10-03\ 05.57.17.xcarchive -exportPath '/var/folders/90/5stft2v13fb_m_gv3c8x9nwc0000gn/T/gym_output20161003-2206-wjhjai'
+ xcodebuild -exportArchive -exportOptionsPlist /var/folders/90/5stft2v13fb_m_gv3c8x9nwc0000gn/T/gym_config20161003-2206-1f0vw3k.plist -archivePath '/Users/vagrant/Library/Developer/Xcode/Archives/2016-10-03/App 2016-10-03 05.57.17.xcarchive' -exportPath /var/folders/90/5stft2v13fb_m_gv3c8x9nwc0000gn/T/gym_output20161003-2206-wjhjai
2016-10-03 06:01:58.299 xcodebuild[5284:14924] [MT] IDEDistribution: -[IDEDistributionLogging _createLoggingBundleAtPath:]: Created bundle at path '/var/folders/90/5stft2v13fb_m_gv3c8x9nwc0000gn/T/App_2016-10-03_06-01-58.298.xcdistributionlogs'.
2016-10-03 06:01:59.596 xcodebuild[5284:14924] [MT] IDEDistribution: Step failed: <IDEDistributionThinningStep: 0x7f868c80f810>: Error Domain=IDEDistributionErrorDomain Code=14 "No applicable devices found." UserInfo={NSLocalizedDescription=No applicable devices found.}
error: exportArchive: No applicable devices found.Error Domain=IDEDistributionErrorDomain Code=14 "No applicable devices found." UserInfo={NSLocalizedDescription=No applicable devices found.}** EXPORT FAILED **
[06:01:59]: Exit status: 70
[06:01:59]: 2016-10-03 13:01:58 +0000 [MT] Running step: IDEDistributionSigningAssetsStep with <IDEDistributionContext: 0x7f868c51ed70; archive(resolved)='<IDEArchive: 0x7f868c4af8d0>', distributionTask(resolved)='2', distributionMethod(resolved)='<IDEDistributionMethodEnterprise: 0x7f868c202a00>', teamID(resolved)='(null)'>
        Chain (2, self inclusive):
        <IDEDistributionContext: 0x7f868c51ed70; archive = '(null)', distributionMethod='<IDEDistributionMethodEnterprise: 0x7f868c202a00>', teamID='(null)'>
        <IDEDistributionContext: 0x7f868c4b0e70; archive = '<IDEArchive: 0x7f868c4af8d0>', distributionMethod='(null)', teamID='(null)'>
</IDEDistributionContext: 0x7f868c51ed70>

This error is misleading: it looks like it might be a code signing error or some configuration issue with fastlane. But if you look further into the error, you may see the following:

2016-10-03 13:01:58 +0000 [MT] Running /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool '/var/folders/90/5stft2v13fb_m_gv3c8x9nwc0000gn/T/IDEDistributionThinningStep.s1x' '--json' '/var/folders/90/5stft2v13fb_m_gv3c8x9nwc0000gn/T/ipatool-json-filepath-RUCdRR' '--info' '--toolchain' '/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr' '--platforms' '/Applications/Xcode.app/Contents/Developer/Platforms'
2016-10-03 13:01:58 +0000  ruby 2.0.0p648 (2015-12-16 revision 53162) [universal.x86_64-darwin15]
2016-10-03 13:01:59 +0000  /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler/definition.rb:181:in `rescue in specs': Your bundle is locked to json (1.8.3), but that version could not be found in any of the sources listed in your Gemfile. If you haven't changed sources, that means the author of json (1.8.3) has removed it. You'll need to update your bundle to a different version of json (1.8.3) that hasn't been removed in order to install. (Bundler::GemNotFound)
        from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler/definition.rb:175:in `specs'
        from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler/definition.rb:235:in `specs_for'
        from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler/definition.rb:224:in `requested_specs'
        from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler/runtime.rb:118:in `block in definition_method'
        from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler/runtime.rb:19:in `setup'
        from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler.rb:99:in `setup'
        from /usr/local/lib/ruby/gems/2.3.0/gems/bundler-1.13.1/lib/bundler/setup.rb:20:in `<top (required)>'
        from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
        from /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/rubygems/core_ext/kernel_require.rb:55:in `require'
2016-10-03 13:01:59 +0000 [MT] /Applications/Xcode.app/Contents/Developer/usr/bin/ipatool exited with 1
2016-10-03 13:01:59 +0000 [MT] ipatool JSON: (null)

What happens is that fastlane reverts back to the Mac OS system's Ruby for exporting. But the system Ruby doesn't have json 1.8.3 installed.

Possible solutions:

Add a Script Step to run the following:

sudo /usr/bin/gem install bundler

This will install bundler on the system Ruby and when the fastlane plugin calls bundle install, then system Ruby will also install the necessary dependencies.