Fix UnboundLocalError during command output substitution

Plugin.do_cmd_output_sub() assumes that the list of executed
commands is non-empty if the list of commands requested is
non-empty. This can be false (e.g. when a command is run
speculatively and the binary is not present) leading to an
unbound variable exception as the code never sets the variable
used as the return value:

Traceback (most recent call last):
File "/usr/sbin/sosreport", line 23, in <module>
main(sys.argv[1:])
File "/usr/lib/python2.7/dist-packages/sos/sosreport.py", line 1154, in main
sos.execute()
UnboundLocalError: local variable 'replacements' referenced before assignment

> /usr/lib/python2.7/dist-packages/sos/plugins/__init__.py(197)do_cmd_output_sub()
-> return replacements

Signed-off-by: Bryn M. Reeves <bmr@redhat.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/sos/plugins/__init__.py b/sos/plugins/__init__.py
index 435d69fe..1a28a1e3 100644
--- a/sos/plugins/__init__.py
+++ b/sos/plugins/__init__.py
@@ -174,6 +174,10 @@ class Plugin(object):
         globstr = '*' + cmd + '*'
         self.soslog.debug("substituting '%s' for '%s' in commands matching %s"
                     % (subst, regexp, globstr))
+
+        if not self.executed_commands:
+            return 0
+
         try:
             for called in self.executed_commands:
                 if fnmatch.fnmatch(called['exe'], globstr):