Make "resource temporarily unavailable" an external error

Do not add Modules issue report web link when facing a "resource
temporarily unavailable" error when forking sub-process like logger or
pager.

Fixes #546

NEWS.rst

@@ -86,7 +86,7 @@ Modules 5.5.0 (not yet released)
   specification as long as the string following them is not a valid variant
   name (e.g., ``foo/1.2+8``). (fix issue #527)
 * In case of an issue external to Modules, do not mention at the end of the
-  error stack trace the web link to report this issue.
+  error stack trace the web link to report this issue. (fix issue #546)
 * When a modulefile performs a :mfcmd:`module unload<module>` command that
   fails due to dependent modules loaded, stop unload evaluation right after
   this failed command unless :option:`--force` option is used.

tcl/report.tcl.in

@@ -2157,6 +2157,7 @@ proc reportFinalError {error_msg} {
          {Can't find a usable init.tcl in the following directories}\
          {interpreter uses an incompatible stubs mechanism}\
          {dlopen(}\
+         {couldn't fork child process: resource temporarily unavailable}\
          {invalid command name "tcl::mathfunc::max"}]
       set add_report_link 1
       foreach external_error $external_error_list {

testsuite/example/siteconfig.tcl-1

@@ -633,5 +633,10 @@ This probably means that Tcl wasn't installed properly.}
 if {[info exists env(TESTSUITE_ENABLE_SITECONFIG_EXTERNALERRORTCLINIT)]} {
     rename tcl::mathfunc::max {}
 }
+if {[info exists env(TESTSUITE_ENABLE_SITECONFIG_EXTERNALERRORRESSOURCEUNAVAIL)]} {
+    proc reportVersion {} {
+        error {couldn't fork child process: resource temporarily unavailable}
+    }
+}
 
 }

testsuite/modules.00-init/120-siteconfig.exp

@@ -690,6 +690,17 @@ lappend ans {  "{*}$execcmdlist"}
 testouterr_cmd sh {avail} ERR [join $ans \n]
 unsetenv_var TESTSUITE_ENABLE_SITECONFIG_EXTERNALERRORTCLINIT
 
+setenv_var TESTSUITE_ENABLE_SITECONFIG_EXTERNALERRORRESSOURCEUNAVAIL 1
+set ans [list]
+lappend ans "$error_msgs: couldn't fork child process: resource temporarily unavailable"
+lappend ans {      while executing}
+lappend ans {  "error {couldn't fork child process: resource temporarily unavailable}"}
+lappend ans {      (procedure "reportVersion" line 2)}
+lappend ans {      invoked from within}
+lappend ans {  "reportVersion"}
+testouterr_cmd sh {-V} ERR [join $ans \n]
+unsetenv_var TESTSUITE_ENABLE_SITECONFIG_EXTERNALERRORRESSOURCEUNAVAIL
+
 
 } elseif {$verbose} {
     send_user "\tSkip tests relying on an excepted siteconfig file installed\n"