In /usr/bin/docbook-to-man line 67:
 $PARSER -gl -m$CATALOG $DECL $INSTANCE |
                              ^-------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
 $PARSER -gl -m$CATALOG $DECL "$INSTANCE" |


In /usr/bin/docbook-to-man line 68:
	$INSTANT -croff.cmap -sroff.sdata -tdocbook-to-man.ts $INSTANT_OPT |
                                                              ^----------^ SC2086: Double quote to prevent globbing and word splitting.

Did you mean: 
	$INSTANT -croff.cmap -sroff.sdata -tdocbook-to-man.ts "$INSTANT_OPT" |

For more information:
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...