minor #14937 Standardize the name of the exception variables (javiereguiluz)

This PR was squashed before being merged into the 2.3 branch (closes #14937).

Discussion
----------

Standardize the name of the exception variables

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

See symfony/symfony-docs#4491 for the context of this change.

In Symfony source code there are 410 `try ... catch` blocks. More than 95% of them use `$e` as the name of the exception variable. After applying these changes, 407 out of 410 variables are named `$e`.

These are the three cases where I didn't change the name of the `$e` variable:

  * Nested exception in https://github.com/symfony/symfony/blob/2.3/src/Symfony/Component/Routing/Matcher/RedirectableUrlMatcher.php#L40. It uses `$e2` as the name of the nested variable.
  * Nested exception in https://github.com/symfony/symfony/blob/2.3/src/Symfony/Bundle/TwigBundle/TwigEngine.php#L82. I changed the name of the `$ex` variable to `$e2` to match the previous syntax.
  * https://github.com/symfony/symfony/blob/2.3/src/Symfony/Component/Console/Helper/DialogHelper.php#L463. I don't know if it's safe to change the name of the `$error` exception variable.

Commits
-------

e8b924c Standardize the name of the exception variables

Author: fabpot

Definition/ArrayNode.php

@@ -256,7 +256,7 @@ protected function finalizeValue($value)
 
             try {
                 $value[$name] = $child->finalize($value[$name]);
-            } catch (UnsetKeyException $unset) {
+            } catch (UnsetKeyException $e) {
                 unset($value[$name]);
             }
         }

Definition/BaseNode.php

@@ -302,14 +302,10 @@ final public function finalize($value)
         foreach ($this->finalValidationClosures as $closure) {
             try {
                 $value = $closure($value);
-            } catch (Exception $correctEx) {
-                throw $correctEx;
-            } catch (\Exception $invalid) {
-                throw new InvalidConfigurationException(sprintf(
-                    'Invalid configuration for path "%s": %s',
-                    $this->getPath(),
-                    $invalid->getMessage()
-                ), $invalid->getCode(), $invalid);
+            } catch (Exception $e) {
+                throw $e;
+            } catch (\Exception $e) {
+                throw new InvalidConfigurationException(sprintf('Invalid configuration for path "%s": %s', $this->getPath(), $e->getMessage()), $e->getCode(), $e);
             }
         }
 

Definition/PrototypedArrayNode.php

@@ -211,7 +211,7 @@ protected function finalizeValue($value)
             $this->prototype->setName($k);
             try {
                 $value[$k] = $this->prototype->finalize($v);
-            } catch (UnsetKeyException $unset) {
+            } catch (UnsetKeyException $e) {
                 unset($value[$k]);
             }
         }