diff --git a/framework/yii/views/errorHandler/exception.php b/framework/yii/views/errorHandler/exception.php
index 4b90de9..426447a 100644
--- a/framework/yii/views/errorHandler/exception.php
+++ b/framework/yii/views/errorHandler/exception.php
@@ -359,7 +359,7 @@ pre .diff .change{
 				}
 			?></h1>
 		<?php endif; ?>
-		<h2><?= $handler->htmlEncode($exception->getMessage()) ?></h2>
+		<h2><?= nl2br($handler->htmlEncode($exception->getMessage())) ?></h2>
 		<?= $handler->renderPreviousExceptions($exception) ?>
 	</div>
 
diff --git a/framework/yii/views/errorHandler/previousException.php b/framework/yii/views/errorHandler/previousException.php
index 5e8ded8..766c0a7 100644
--- a/framework/yii/views/errorHandler/previousException.php
+++ b/framework/yii/views/errorHandler/previousException.php
@@ -15,7 +15,7 @@
 			<span><?= $handler->htmlEncode(get_class($exception)) ?></span>
 		<?php endif; ?>
 	</h2>
-	<h3><?= $handler->htmlEncode($exception->getMessage()) ?></h3>
+	<h3><?= nl2br($handler->htmlEncode($exception->getMessage())) ?></h3>
 	<p>in <span class="file"><?= $exception->getFile() ?></span> at line <span class="line"><?= $exception->getLine() ?></span></p>
 	<?= $handler->renderPreviousExceptions($exception) ?>
 </div>
diff --git a/framework/yii/web/AssetConverter.php b/framework/yii/web/AssetConverter.php
index 3b654e5..ba64aa9 100644
--- a/framework/yii/web/AssetConverter.php
+++ b/framework/yii/web/AssetConverter.php
@@ -9,6 +9,7 @@ namespace yii\web;
 
 use Yii;
 use yii\base\Component;
+use yii\base\Exception;
 
 /**
  * AssetConverter supports conversion of several popular script formats into JS or CSS scripts.
@@ -24,7 +25,7 @@ class AssetConverter extends Component implements AssetConverterInterface
 	 * target script types (either "css" or "js") and the commands used for the conversion.
 	 */
 	public $commands = [
-		'less' => ['css', 'lessc {from} {to}'],
+		'less' => ['css', 'lessc {from} {to} --no-color'],
 		'scss' => ['css', 'sass {from} {to}'],
 		'sass' => ['css', 'sass {from} {to}'],
 		'styl' => ['js', 'stylus < {from} > {to}'],
@@ -82,10 +83,12 @@ class AssetConverter extends Component implements AssetConverterInterface
 		}
 		$status = proc_close($proc);
 
-		if ($status !== 0) {
-			Yii::error("AssetConverter command '$command' failed with exit code $status:\nSTDOUT:\n$stdout\nSTDERR:\n$stderr\n");
-		} else {
+		if ($status === 0) {
 			Yii::trace("Converted $asset into $result:\nSTDOUT:\n$stdout\nSTDERR:\n$stderr", __METHOD__);
+		} elseif (YII_DEBUG) {
+			throw new Exception("AssetConverter command '$command' failed with exit code $status:\nSTDOUT:\n$stdout\nSTDERR:\n$stderr");
+		} else {
+			Yii::error("AssetConverter command '$command' failed with exit code $status:\nSTDOUT:\n$stdout\nSTDERR:\n$stderr");
 		}
 		return $status === 0;
 	}