fix consistency in binary execution and existance checking

 - prefer using `which` over hard coded paths
 - it is redundant to check that the bin pointed to the return of
   `which` exists and is executable, `which` already gives us
   assurance of that if it returns true!
 - the redirection of output (`2>/dev/null`) seems to be
   unnecessary from my testing.

the instances relatnig to fdisk and losetup in functions/defaults.sh have
been left as they are since they get executed by `lb config` which can run
without sudo elevation unlike `lb build` and in that case `which` would
fail to find these binaries resulting in error.

this also fixes a bug showing an error for missing debootstrap - this tool
requires sudo privileges to run and thus is not found via a none elevated
which search.

Gbp-Dch: Short
Closes: #952927

1 files changed, 2 insertions, 2 deletions

diff --git a/share/bin/Packages b/share/bin/Packages
index fa6cbbaa2..185fba78d 100755
--- a/share/bin/Packages
+++ b/share/bin/Packages
@@ -10,9 +10,9 @@
 
 set -e
 
-if [ ! -e /usr/bin/grep-aptavail ]
+if [ ! $(which grep-aptavail) ]
 then
-	echo "E: /usr/bin/grep-aptavail: No such file."
+	echo "E: program grep-aptavail not found!"
 
 	exit 1
 fi