title: Why does fastlane add_badge work for me locally but fail on App Center
body: <p>As per the title, if I execute the following (for example) from my local machine, the command succeeds and all my icons get updated correctly:</p>
  
  <p><code>fastlane addBadge branch_name:staging build_number:1558591886 branch_color:green</code></p>
  
  <p>However, when the build runs on Visual Studio App Center, it errors with the following output:</p>
  
  <pre><code>[32mDriving the lane 'addBadge' [0m
  [06:46:53]: [32m-----------------------[0m
  [06:46:53]: [32m--- Step: add_badge ---[0m
  [06:46:53]: [32m-----------------------[0m
  [06:46:53]: [32mStart adding badges...[0m
  [06:46:54]: './iOS/Assets.xcassets/AppIcons.appiconset/icon120x120.png'
  dyld: Symbol not found: _OBJC_CLASS_$_NSFont
    Referenced from: /Library/Frameworks/Mono.framework/Versions/5.18.1/lib/libpangocairo-1.0.0.dylib
    Expected in: flat namespace
   in /Library/Frameworks/Mono.framework/Versions/5.18.1/lib/libpangocairo-1.0.0.dylib
  +---------------+----------+
  |       [33mLane Context[0m       |
  +---------------+----------+
  | PLATFORM_NAME |          |
  | LANE_NAME     | addBadge |
  +---------------+----------+
  [06:46:54]: [31mNo such file or directory @ rb_sysopen - 1558593854-staging-green.svg.png[0m
  </code></pre>
  
  <p><br/></p>
  
  <p>For App Center, I'm calling the <code>fastlane addBadge</code> command from <code>appcenter-pre-build.sh</code>.</p>
  
  <p><strong>Question:</strong> Why is this error happening, what do I do to fix it?</p>
  
  <p><strong>Update 1:</strong> After adding <code>--verbose</code> to the <code>addBadge</code> command:</p>
  
  <p>Here's what I get locally:</p>
  
  <pre><code>Driving the lane 'addBadge' 
  INFO [2019-05-24 09:58:54.78]: -----------------------
  INFO [2019-05-24 09:58:54.78]: --- Step: add_badge ---
  INFO [2019-05-24 09:58:54.78]: -----------------------
  INFO [2019-05-24 09:58:54.86]: gem 'badge' is already installed
  WARN [2019-05-24 09:58:54.87]: Install RSVG to get better results for shields on top of your icon
  WARN [2019-05-24 09:58:54.87]: 
  WARN [2019-05-24 09:58:54.87]: Install it using (RSVG):
  INFO [2019-05-24 09:58:54.87]: $ brew install librsvg
  WARN [2019-05-24 09:58:54.87]: 
  DEBUG [2019-05-24 09:58:54.88]: Verbose active... VERSION: 0.10.0
  DEBUG [2019-05-24 09:58:54.88]: Parameters: {:shield=&gt;"1558591886-staging-green", :no_badge=&gt;true, :glob=&gt;"{/iOS/Assets.xcassets/AppIcons.appiconset/*.{png,PNG},/Droid/Resources/**/{icon}.{png,PNG}}", :dark=&gt;nil, :alpha=&gt;nil, :alpha_channel=&gt;nil, :custom=&gt;nil, :badge_gravity=&gt;nil, :shield_parameters=&gt;nil, :shield_io_timeout=&gt;nil, :shield_geometry=&gt;nil, :shield_gravity=&gt;nil, :shield_scale=&gt;nil, :shield_no_resize=&gt;nil, :grayscale=&gt;false}
  INFO [2019-05-24 09:58:54.88]: Start adding badges...
  DEBUG [2019-05-24 09:58:54.88]: Trying to load image from shields.io. Timeout: 10s
  DEBUG [2019-05-24 09:58:54.88]: URL: https://img.shields.io/badge/1558591886-staging-green.png
  INFO [2019-05-24 09:58:56.36]: './iOS/Assets.xcassets/AppIcons.appiconset/icon120x120.png'
  DEBUG [2019-05-24 09:58:56.36]: Adding shields.io image ontop of icon
  INFO [2019-05-24 09:58:56.43]: './iOS/Assets.xcassets/AppIcons.appiconset/icon58x58.png'
  </code></pre>
  
  <p><br/>
  And here's what's outputted on App Center:</p>
  
  <pre><code>INFO [2019-05-24 00:13:28.42]: [32mDriving the lane 'addBadge' [0m
  INFO [2019-05-24 00:13:28.43]: [32m-----------------------[0m
  INFO [2019-05-24 00:13:28.43]: [32m--- Step: add_badge ---[0m
  INFO [2019-05-24 00:13:28.43]: [32m-----------------------[0m
  INFO [2019-05-24 00:13:28.50]: [32mgem 'badge' is already installed[0m
  DEBUG [2019-05-24 00:13:28.51]: [34mVerbose active... VERSION: 0.10.0[0m
  DEBUG [2019-05-24 00:13:28.51]: [34mParameters: {:shield=&gt;"1558656638-staging-green", :no_badge=&gt;true, :glob=&gt;"{/iOS/Assets.xcassets/AppIcons.appiconset/*.{png,PNG},/Droid/Resources/**/{icon}.{png,PNG}}", :dark=&gt;nil, :alpha=&gt;nil, :alpha_channel=&gt;nil, :custom=&gt;nil, :badge_gravity=&gt;nil, :shield_parameters=&gt;nil, :shield_io_timeout=&gt;nil, :shield_geometry=&gt;nil, :shield_gravity=&gt;nil, :shield_scale=&gt;nil, :shield_no_resize=&gt;nil, :grayscale=&gt;false}[0m
  INFO [2019-05-24 00:13:28.51]: [32mStart adding badges...[0m
  DEBUG [2019-05-24 00:13:28.51]: [34mTrying to load image from shields.io. Timeout: 10s[0m
  DEBUG [2019-05-24 00:13:28.51]: [34mURL: https://img.shields.io/badge/1558656638-staging-green.svg[0m
  INFO [2019-05-24 00:13:29.27]: './iOS/Assets.xcassets/AppIcons.appiconset/icon120x120.png'
  DEBUG [2019-05-24 00:13:29.27]: [34mAdding shields.io image ontop of icon[0m
  dyld: Symbol not found: _OBJC_CLASS_$_NSFont
    Referenced from: /Library/Frameworks/Mono.framework/Versions/5.12.0/lib/libpangocairo-1.0.0.dylib
    Expected in: flat namespace
   in /Library/Frameworks/Mono.framework/Versions/5.12.0/lib/libpangocairo-1.0.0.dylib
  WARN [2019-05-24 00:13:29.34]: [33m[33mLane Context:[0m
  INFO [2019-05-24 00:13:29.34]: {:PLATFORM_NAME=&gt;nil, :LANE_NAME=&gt;"addBadge"}
  ERROR [2019-05-24 00:13:29.34]: [31mNo such file or directory @ rb_sysopen - 1558656638-staging-green.svg.png[0m
  </code></pre>
  
  <p><br/>
  It seems like on the build agent, an svg is being requested instead of a png. Could that have something to do with it?</p>