about: add Troubleshooting to GnuPG usage

dist/templates/about/usage.html.hbs

@@ -70,7 +70,7 @@
         </blockquote>
     </p>
 
-    <h4>Retrieving keys</h4>
+    <h4 id="gnupg-retrieve"><a href="#gnupg-retrieve">Retrieving keys</a></h4>
     <ul>
         <li>
             To locate the key of a user, by email address:
@@ -78,10 +78,6 @@
         </li>
         <li>To refresh all your keys (e.g. new revocation certificates and subkeys):
             <blockquote>gpg --refresh-keys</blockquote>
-            <b>Note:</b> If you see errors like the following,
-            see <a href="/about/faq#older-gnupg">our notes</a> on compatibility
-            with older versions of GnuPG.
-            <blockquote>gpg: key A2604867523C7ED8: no user ID</blockquote>
         </li>
     </ul>
 
@@ -109,7 +105,28 @@
         </li>
     </ul>
 
-    <h4>Usage via Tor</h4>
+    <h4 id="gnupg-troubleshooting"><a href="#gnupg-troubleshooting">Troubleshooting</a></h4>
+    <ul>
+        <li>
+            Some old <tt>~/gnupg/dirmngr.conf</tt> files contain a line like this:
+            <blockquote>
+                hkp-cacert ~/.gnupg/sks-keyservers.netCA.pem
+            </blockquote>
+            <p>
+                This configuration is no longer necessary,
+                but prevents regular certificates from working.
+                It is recommended to simply remove this line from the configuration.
+            </p>
+        </li>
+        <li>
+            While refreshing keys, you may see errors like the following:
+            <blockquote>gpg: key A2604867523C7ED8: no user ID</blockquote>
+            This is a <a href="https://dev.gnupg.org/T4393" target="_blank">known problem in GnuPG</a>.
+            We are working with the GnuPG team to resolve this issue.
+        </li>
+    </ul>
+
+    <h4 id="gnupg-tor"><a href="#gnupg-tor">Usage via Tor</a></h4>
     <p>
         For users who want to be extra-careful,
         <span class="brand">keys.openpgp.org</span> can be reached anonymously as an