minor #29928 [DependencyInjection] forward the parse error to the calling code (xabbuh)

This PR was merged into the 3.4 branch.

Discussion
----------

[DependencyInjection] forward the parse error to the calling code

| Q             | A
| ------------- | ---
| Branch?       | 3.4
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #29891
| License       | MIT
| Doc PR        |

This change does not fully solve the linked issue, but improves the exception a bit by providing a bit more context.

The error page will no start like this:

![bildschirmfoto 2019-01-18 um 12 28 14](https://user-images.githubusercontent.com/1957048/51384558-f7af3600-1b1c-11e9-9744-a40c41c821ce.png)

Commits
-------

c5c2d31fef forward the parse error to the calling code

src/Symfony/Component/DependencyInjection/Loader/XmlFileLoader.php

@@ -383,7 +383,7 @@ class XmlFileLoader extends FileLoader
         try {
             $dom = XmlUtils::loadFile($file, [$this, 'validateSchema']);
         } catch (\InvalidArgumentException $e) {
-            throw new InvalidArgumentException(sprintf('Unable to parse file "%s".', $file), $e->getCode(), $e);
+            throw new InvalidArgumentException(sprintf('Unable to parse file "%s": %s', $file, $e->getMessage()), $e->getCode(), $e);
         }
 
         $this->validateExtensions($dom, $file);

src/Symfony/Component/DependencyInjection/Loader/YamlFileLoader.php

@@ -666,7 +666,7 @@ class YamlFileLoader extends FileLoader
         try {
             $configuration = $this->yamlParser->parseFile($file, Yaml::PARSE_CONSTANT | Yaml::PARSE_CUSTOM_TAGS);
         } catch (ParseException $e) {
-            throw new InvalidArgumentException(sprintf('The file "%s" does not contain valid YAML.', $file), 0, $e);
+            throw new InvalidArgumentException(sprintf('The file "%s" does not contain valid YAML: %s', $file, $e->getMessage()), 0, $e);
         } finally {
             restore_error_handler();
         }