Override the error page so we can apply branding (#313)

The default error page uses the govuk branding (and not the unbranded
version) and so we have no control over what it looks like.  With
previously installed packages, we get the wrong logo etc.

Author: rossjones

lib/importer/nunjucks/views/error-handling/page-not-found.njk

@@ -0,0 +1,29 @@
+{% extends "layouts/main.html" %}
+
+{% block pageTitle %}
+  Page not found – {{ serviceName }} – GOV.UK Prototype Kit
+{% endblock %}
+{% set mainClasses = "govuk-main-wrapper--l" %}
+
+{% block content %}
+
+  <div class="govuk-grid-row">
+    <div class="govuk-grid-column-two-thirds">
+
+      <h1 class="govuk-heading-l">Page not found</h1>
+      <p class="govuk-body">
+        There is no page at <strong>{{ path }}</strong>
+      </p>
+      <p class="govuk-body">This may be because:</p>
+      <ul class="govuk-list govuk-list--bullet">
+        <li>you typed or pasted the web address incorrectly</li>
+        <li>a link in your code is wrong</li>
+        <li>a form in your code is wrong</li>
+        <li>you have not created the page yet</li>
+      </ul>
+      <p class="govuk-body">
+            You can try and fix this yourself or <a class="govuk-link" href="https://www.register-dynamics.co.uk/contacts">contact the Register Dynamics team</a> if you need help.
+        </p>
+    </div>
+  </div>
+{% endblock %}

lib/importer/nunjucks/views/error-handling/server-error.njk

@@ -0,0 +1,72 @@
+{% extends "layouts/main.html" %}
+
+{% block pageTitle %}
+  Error {% if serviceName %}– {{ serviceName }}{% endif %} – GOV.UK Prototype Kit
+{% endblock %}
+
+{% block content %}
+
+  <div class="govuk-grid-row">
+    <div class="govuk-grid-column-full">
+      <h1 class="govuk-heading-l">There is an error</h1>
+
+      {% if error.filePath %}
+      <p class="govuk-prototype-kit-error-info">
+        <strong>File:</strong> <span id="govuk-prototype-kit-error-file">{{ error.filePath }} {%  if error.line %}(line {{ error.line }}){% endif %}</span>
+      </p>
+      {% endif %}
+
+      <p class="govuk-prototype-kit-error-info">
+        <strong>Error:</strong> <span id="govuk-prototype-kit-error-message">{{ error.message }}</span>
+      </p>
+
+      {% if error.sourceCode %}
+      <pre tabindex="0" class="govuk-prototype-kit-error-code govuk-!-margin-bottom-5" id="govuk-prototype-kit-error-block"><code>{{ error.sourceCode.before }}</code><br><code id="govuk-prototype-kit-error-line">{{ error.sourceCode.error }}</code><br><code>{{ error.sourceCode.after }}</code></pre>
+      {% endif %}
+
+      <div id="govuk-prototype-kit-show-error-button-container" hidden>
+        <button id="govuk-prototype-kit-show-error-button" class="govuk-button govuk-button--secondary govuk-!-margin-bottom-1" data-module="govuk-button" aria-expanded="false" aria-controls="govuk-prototype-kit-error-stack">
+          Show full error
+        </button>
+      </div>
+
+      <pre tabindex="0" id="govuk-prototype-kit-error-stack" class="govuk-prototype-kit-error-code js-hidden"><code>{{ error.errorStack }}</code></pre>
+
+      <p class="govuk-body govuk-!-margin-top-5">
+        <a class="govuk-link" href="https://www.register-dynamics.co.uk/contact">Get support</a>
+      </p>
+
+    </div>
+  </div>
+
+
+{% endblock %}
+
+
+{% block footer %}
+  {{ govukFooter({}) }}
+{% endblock %}
+
+
+{% block pageScripts %}
+<script>
+  ;(() => {
+    const toggleErrorStack = (event) => {
+      const button = event.target
+      const isExpanded = button.getAttribute('aria-expanded') === 'true'
+      const newState = isExpanded ? 'false' : 'true'
+      const newText = isExpanded ? 'Show full error' : 'Hide full error'
+      button.setAttribute('aria-expanded', newState)
+      button.textContent = newText
+
+      const element = document.getElementById('govuk-prototype-kit-error-stack')
+      element.classList.toggle('js-hidden')
+    }
+
+    document.getElementById('govuk-prototype-kit-show-error-button-container').hidden = false
+
+    document.getElementById('govuk-prototype-kit-show-error-button')
+            .addEventListener('click', toggleErrorStack)
+  })()
+</script>
+{% endblock %}