Improved text of exception message in case of error in module's composer.json

[vovayatsyuk]

Description

When some third-party module has syntax error inside its composer.json, it's very hard to determine which
module caused an exception.

This PR changes default message with the following:

Some_Module's composer.json error: Decoding failed: Syntax error

where Decoding failed: Syntax error - is a message of the original exception

Manual testing scenarios

Sample data must be installed to test this behavior.

1. Make an error in app/code/Magento/Cms/composer.json:

2. Run php bin/magento sampeladata:reset. You'll receive a message:

   [Zend_Json_Exception]          
   Decoding failed: Syntax error
   

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)

[adragus-inviqa]

I wouldn't concat any other string with the module name; it'd keep it completely separate, to make it more obvious.
Something likeError decoding composer.json for module Some_Module.

[vovayatsyuk]

I'd like to keep original exception message without change, because there are multiple possible variants for it. So we need a template that will suite for all kind of messages.

[adragus-inviqa]

I'm not sure what you mean by "a template that will suite for all kind of messages"; it just has to be a good format.

But your recent change looks good. I just didn't like the interpolation: $moduleName's.

[magento-team]

@vovayatsyuk thank you for your contribution. Your Pull Request has been successfully merged