lint: Add rule for spacing inside Handlebars translation tags.

This commit also includes the fixes to make all Handlebars templates
compliant with the new rule.

static/templates/settings/bot-list-admin.handlebars

@@ -15,7 +15,7 @@
     <div class="progressive-table-wrapper">
         <table class="table table-condensed table-striped wrapped-table">
             <tbody id="admin_bots_table" class="admin_bot_table required-text thick"
-                   data-empty="{{ t 'No bots match your current filter.' }}"></tbody>
+                   data-empty="{{t 'No bots match your current filter.' }}"></tbody>
         </table>
     </div>
     <div id="admin_page_bots_loading_indicator"></div>

static/templates/settings/bot-settings.handlebars

@@ -5,7 +5,7 @@
         </div>
 
         <div>
-            <span>{{ t 'Download config of all active outgoing webhook bots in Zulip Botserver format.' }}</span>
+            <span>{{t 'Download config of all active outgoing webhook bots in Zulip Botserver format.' }}</span>
             <a type="submit" download="{{flaskbotrc}}" id= "download_flaskbotrc" class="btn" title="{{t 'Download flaskbotrc' }}">
                 <i class="icon-vector-download-alt sea-green"></i>
             </a>

tools/linter_lib/custom_check.py

@@ -389,6 +389,8 @@ def build_custom_checkers(by_lang):
     handlebars_rules = html_rules + [
         {'pattern': "[<]script",
          'description': "Do not use inline <script> tags here; put JavaScript in static/js instead."},
+        {'pattern': '{{ t ("|\')',
+         'description': 'There should be no spaces before the "t" in a translation tag.'},
         {'pattern': "{{t '.*' }}[\.\?!]",
          'description': "Period should be part of the translatable string."},
         {'pattern': '{{t ".*" }}[\.\?!]',