1 files changed, 46 insertions, 46 deletions
diff --git a/Master/texmf-dist/source/latex/l3kernel/l3file.dtx b/Master/texmf-dist/source/latex/l3kernel/l3file.dtx
index bbfd23957f4..67d708da28a 100644
--- a/Master/texmf-dist/source/latex/l3kernel/l3file.dtx
+++ b/Master/texmf-dist/source/latex/l3kernel/l3file.dtx
@@ -44,7 +44,7 @@
 %    }^^A
 % }
 %
-% \date{Released 2020-09-03}
+% \date{Released 2020-09-06}
 %
 % \maketitle
 %
@@ -3597,37 +3597,43 @@
         kpsewhich ~ --all ~
           --engine = \c_sys_engine_exec_str
           \c_space_tl \c_sys_engine_format_str
-            \tl_if_empty:NF \development@branch@name { -dev } .fmt
+            \bool_lazy_and:nnF
+                { \tl_if_exist_p:N \development@branch@name }
+                { ! \tl_if_empty_p:N \development@branch@name }
+              { -dev } .fmt
       }
     \seq_clear:N \l_@@_tmp_seq
     \ior_map_inline:Nn \g_@@_internal_ior
       { \seq_put_right:Nn \l_@@_tmp_seq {##1} }
     \ior_close:N \g_@@_internal_ior
+    \__kernel_msg_error:nnnn { kernel } { mismatched-support-file }
+      {#1} {#2}
 %    \end{macrocode}
-%   Now define a some shorthands so that we can use \cs{@latex@error}
-%   (almost) easily:
+%   And finish by ending the current file.
 %    \begin{macrocode}
-    \group_begin:
-      \cs_set:Npn \\ { \MessageBreak }
-      \cs_set_eq:NN \  \c_space_tl
-      \@latex@error
-        {
-          Mismatched~LaTeX~support~files~detected. \\
-          Loading~'#2'~aborted!
+    \tex_endinput:D
+  }
+%    \begin{macrocode}
+%
+%   Now define the actual error message:
+%    \begin{macrocode}
+\__kernel_msg_new:nnnn { kernel } { mismatched-support-file }
+  {
+    Mismatched~LaTeX~support~files~detected. \\
+    Loading~'#2'~aborted!
 %    \end{macrocode}
 %   \cs{c__kernel_expl_date_tl} may not exist, due to an older format,
 %   so only print the dates when the sentinel token list exists:
 %    \begin{macrocode}
-          \tl_if_exist:NT \c__kernel_expl_date_tl
-            {
-              \\ \\
-              The~L3~programming~layer~in~the~LaTeX~format \\
-              is~dated~\c__kernel_expl_date_tl,~but~in~your~TeX~
-              tree~the~files~require \\ at~least~#1.
-            }
-          \use_none:n
-        }
-        {
+    \tl_if_exist:NT \c__kernel_expl_date_tl
+      {
+        \\ \\
+        The~L3~programming~layer~in~the~LaTeX~format \\
+        is~dated~\c__kernel_expl_date_tl,~but~in~your~TeX~
+        tree~the~files~require \\ at~least~#1.
+      }
+  }
+  {
 %    \end{macrocode}
 %   The sequence containing the format files should have exactly one
 %   item: the format file currently being run.  If that's the case, the
@@ -3636,31 +3642,25 @@
 %   the list to the user, with appropriate indications of what's in the
 %   system and what's in the user tree.
 %    \begin{macrocode}
-          \int_compare:nNnTF { \seq_count:N \l_@@_tmp_seq } > 1
-            {
-              The~cause~seems~to~be~an~old~format~file~in~the~user~tree. \\
-              LaTeX~found~these~files:
-              \seq_map_tokens:Nn \l_@@_tmp_seq { \\~-~\use:n } \\
-              Try~deleting~the~file~in~the~user~tree~then~run~LaTeX~again.
-            }
-            {
-              The~most~likely~causes~are:
-              \\~-~A~recent~format~generation~failed;
-              \\~-~A~stray~format~file~in~the~user~tree~which~needs~
-                   to~be~removed~or~rebuilt;
-              \\~-~You~are~running~a~manually~installed~version~of~#2 \\
-              \ \ \ which~is~incompatible~with~the~version~in~LaTeX. \\
-            }
-          \\
-          LaTeX~will~abort~loading~the~incompatible~support~files~
-          but~this~may~lead~to \\ later~errors.~Please~ensure~that~
-          your~LaTeX~format~is~correctly~regenerated.
-        }
-    \group_end:
-%    \end{macrocode}
-%   And finish by ending the current file.
-%    \begin{macrocode}
-    \tex_endinput:D
+    \int_compare:nNnTF { \seq_count:N \l_@@_tmp_seq } > 1
+      {
+        The~cause~seems~to~be~an~old~format~file~in~the~user~tree. \\
+        LaTeX~found~these~files:
+        \seq_map_tokens:Nn \l_@@_tmp_seq { \\~-~\use:n } \\
+        Try~deleting~the~file~in~the~user~tree~then~run~LaTeX~again.
+      }
+      {
+        The~most~likely~causes~are:
+        \\~-~A~recent~format~generation~failed;
+        \\~-~A~stray~format~file~in~the~user~tree~which~needs~
+             to~be~removed~or~rebuilt;
+        \\~-~You~are~running~a~manually~installed~version~of~#2 \\
+        \ \ \ which~is~incompatible~with~the~version~in~LaTeX. \\
+      }
+    \\
+    LaTeX~will~abort~loading~the~incompatible~support~files~
+    but~this~may~lead~to \\ later~errors.~Please~ensure~that~
+    your~LaTeX~format~is~correctly~regenerated.
   }
 %    \end{macrocode}
 % \end{macro}