Better error messages when component can't be loaded

[chapulina]

Signed-off-by: Louise Poubel [email protected]

Related to #30

Summary

It's often difficult to find out why a QML file failed to load. With this PR we get more verbose error messages that should help users identify problems more easily.

For example, I was debugging some code where I was getting this message:

[GUI] [Err] [Plugin.cc:136] Failed to instantiate QML file [:/Scene3D/Scene3D.qml].
* Are you sure it's been added to the .qrc file?
* Are you sure the file is valid QML? You can check with the `qmlscene` tool

With this PR, I get this message:

[GUI] [Err] [Plugin.cc:146] Failed to instantiate QML file [:/Scene3D/Scene3D.qml].
* file::/Scene3D/Scene3D.qml:19:1: module "RenderWindow" is not installed

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See
  contributing)
• All tests passed (See
  test coverage)
• [ x While waiting for a review on your PR, please help review
  another open pull request
  to support the maintainers

Note to maintainers: Remember to use Squash-Merge

[codecov]

Codecov Report

Merging #175 (ea59762) into ign-gui3 (7863c80) will decrease coverage by 0.24%.
The diff coverage is 17.64%.

@@             Coverage Diff              @@
##           ign-gui3     #175      +/-   ##
============================================
- Coverage     59.12%   58.87%   -0.25%     
============================================
  Files            21       21              
  Lines          2608     2624      +16     
============================================
+ Hits           1542     1545       +3     
- Misses         1066     1079      +13     

Impacted Files	Coverage Δ
src/Plugin.cc	57.44% <17.64%> (-2.83%)	⬇️

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[ahcorde]

+1 Really usefull to know where is the error in the QML