Merge #806: download: fix outdated use of page.obtain_release_key

f64df66 test: ensure template strings don't leak through liquid (James O'Beirne)
60dae23 download: fix outdated use of page.obtain_release_key (James O'Beirne)

Pull request description:

  Ironically, @harding's comment in #803 (comment) was spot on. This fixes a lingering reference to `$(BUILDER_KEYS_TXT_URL)` in the macOS and Linux instructions.

ACKs for top commit:
  harding:
    Tested ACK f64df66 . Fixes a broken link and adds a useful test.  Thanks!

Tree-SHA512: 8ec35d8f4438133165970706e7ba632c4e94a0e1abced568fe0584a393ebf37bdf2681e1a76ea3dd2de8c27b26a6212d35b750754415d86b0b0147f0092b1a3b

Author: harding

Makefile

@@ -19,3 +19,5 @@ test-slow:
 test-fast:
 	## Check for broken Markdown reference-style links that are displayed in text unchanged, e.g. [broken][broken link]
 	! find _site/ -name '*.html' | xargs grep ']\[' | grep -v skip-test | grep .
+	## Ensure that no template strings leak through liquid rendering
+	! find _site/ -name '*.html' | xargs grep '\$$(.*)'

_includes/templates/download.html

@@ -186,7 +186,7 @@ <h2 style="text-align: center" id="{{page.verify_download | slugify}}">{{page.ve
       {{page.gpg_download_other}}
       <a href="{{GPG_DOWNLOAD_URL}}">{{page.gpg_download_options}}</a></p></li>
 
-      <li><p>{{page.obtain_release_key | replace: '$(BUILDER_KEYS_URL)', page.builder_keys_url | replace: '$(EXAMPLE_BUILDERS_LINE)', page.example_builders_line}}</p>
+      <li><p>{{OBTAIN_RELEASE_KEY}}</p>
 
         <pre class="highlight"><code>gpg{{site.strings.gpg_keyserver}} --recv-keys {{example_builder_key}}</code></pre>
 
@@ -228,7 +228,7 @@ <h2 style="text-align: center" id="{{page.verify_download | slugify}}">{{page.ve
 
         <p>{{page.checksum_warning_and_ok | replace, "$(SHASUMS_OK)", page.localized_checksum_ok}} <code>{{FILE_PREFIX}}-{{site.data.binaries.lin64}}: {{page.localized_checksum_ok}}</code></p></li>
 
-      <li><p>{{page.obtain_release_key | replace: '$(BUILDER_KEYS_URL)', page.builder_keys_url | replace: '$(EXAMPLE_BUILDERS_LINE)', page.example_builders_line}}</p>
+      <li><p>{{OBTAIN_RELEASE_KEY}}</p>
 
         <pre class="highlight"><code>gpg{{site.strings.gpg_keyserver}} --recv-keys {{example_builder_key}}</code></pre>