Added custom error pages, that assists users with common problems.

templates/bundles/TwigBundle/Exception/assets/error.css.twig

@@ -0,0 +1,95 @@
+body {
+    background-color: #fff;
+    color: #222;
+    font: 16px/1.5 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
+    margin: 0;
+}
+.container {
+    padding: 50px;
+    width: 100%;
+    box-sizing: border-box;
+}
+
+h1 {
+    margin-top: 10px;
+    color: #dc3545;
+    font-size: 24px;
+}
+h2 {
+    font-size: 18px;
+}
+
+.status_code {
+    text-align: center;
+
+    font-size: 72px;
+    line-height: 0.5;
+}
+
+.status_text {
+    text-align: center;
+    line-height: 0.5;
+    font-size: 32px;
+}
+
+.status_comment {
+    text-align: center;
+    line-height: 1;
+}
+
+.help_text {
+    text-align: center;
+    font-size: 18px;
+}
+
+.text-muted {
+    color: #6c757d!important;
+}
+
+.text-center {
+    text-align: center;
+}
+
+ul {
+    display: table;
+    margin: 10px auto;
+    line-height: 1.4;
+    text-align: left;
+}
+
+.footer {
+    box-sizing: border-box;
+    position: absolute;
+    bottom: 0;
+    width: 100%;
+    height: 60px;
+    line-height: 1.2;
+    text-align: left;
+    padding-top: 15px;
+    padding-left: 30px;
+    background-color: #f5f5f5;
+}
+
+.dev_hint {
+    margin-top: 45px;
+    line-height: 0.5;
+    text-align: center;
+}
+
+code {
+    font-size: 87.5%;
+    color: #e83e8c;
+    word-break: break-word;
+}
+
+code, kbd, pre, samp {
+    font-family: SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace;
+}
+
+kbd {
+    padding: .2rem .4rem;
+    font-size: 87.5%;
+    color: #fff;
+    background-color: #212529;
+    border-radius: .2rem;
+}