Improve known issue (#17792)

- Explain the actual symptoms (the password will always be rejected) and
  avoid an ambiguous use of a modal verb ('cannot').
- Explain the workaround: people might loose work if they realize half
  way through their session that they cannot install an Additional
  Software.
- I don't expect the command line trick to be very useful.
- Link to what our terminology means ('administration password').
- Clarify what non-English means.

wiki/src/news/version_4.8.mdwn

@@ -72,13 +72,23 @@ For more details, read our [[!tails_gitweb debian/changelog desc="changelog"]].
 
 # Known issues
 
-* Administration passwords set at the Welcome Screen cannot contain
-  most non-english characters, including spaces ([[!tails_ticket
-  17792]]). Because of this you should limit your passwords to only
-  alphanumeric characters (`a-z`, `A-Z`, `0-9`) and the following
-  special characters: `_@%+=:,./-`. Once you have logged in you can
-  change the password however you like using the `passwd` command in a
-  Terminal.
+* Only use the following characters in the [[administration
+  password|doc/first_steps/welcome_screen/administration_password]]:
+
+  - <span class="code">a&ndash;z</span>
+  - <span class="code">A&ndash;Z</span>
+  - <span class="code">1&ndash;9</span>
+  - <span class="code">_@%+=:,./-</span>
+
+  If you use spaces or other accentuated characters, like <span
+  class="code">àéïøů</span>, your will not be able to type your
+  administration password again in your Tails session, unless you
+  type single quotes <span class="code">'</span> around it.
+
+  For example, if you set the administration password:
+  <span class="code">née entrepôt über señor</span>, you would have to
+  type <span class="code">'née entrepôt über señor'</span>.
+  ([[!tails_ticket 17792]])
 
 See the list of [[long-standing issues|support/known_issues]].