api: check apt exitcode for unexpected value

api

@@ -371,8 +371,9 @@ apt_update() { #run an apt update with error-checking and minimal output
   apt_lock_wait
 
   status "Running \e[7msudo apt update\e[27m..."
-  output="$(sudo -E apt update --allow-releaseinfo-change "$@" 2>&1 | less_apt | tee /dev/stderr)"
-  exitcode=$?
+  set -o pipefail
+  local output="$(sudo -E apt update --allow-releaseinfo-change "$@" 2>&1 | less_apt | tee /dev/stderr)"
+  local exitcode=$?
   status "apt update complete."
 
   #inform user about autoremovable packages
@@ -388,7 +389,7 @@ apt_update() { #run an apt update with error-checking and minimal output
   fi
 
   #exit on apt error
-  errors="$(echo "$output" | grep '^[(E)|(Err]:')"
+  local errors="$(echo "$output" | grep '^[(E)|(Err]:')"
   if [ $exitcode != 0 ] || [ ! -z "$errors" ];then
     echo -e "\e[91mFailed to run \e[4msudo apt update\e[0m\e[39m!"
     echo -e "APT reported these errors:\n\e[91m$errors\e[39m"
@@ -674,7 +675,9 @@ Package: $package_name" > /tmp/$package_name/DEBIAN/control
       status "Installing the $package_name package..."
 
       apt_lock_wait
+      set -o pipefail
       local output="$(sudo -E apt install -fy --no-install-recommends --allow-downgrades "${apt_flags[@]}" /tmp/$package_name.deb 2>&1 | less_apt | tee /dev/stderr)"
+      local exitcode=$?
       status "Apt finished."
 
       if [ "$using_local_packages" == 1 ] && [ ! -f /var/lib/apt/lists/_tmp_pi-apps-local-packages_._Packages ] && [ $i != 5 ];then
@@ -687,12 +690,13 @@ Package: $package_name" > /tmp/$package_name/DEBIAN/control
       fi
     done
 
-    errors="$(echo "$output" | grep '^[(E)|(Err]:')"
-    if [ ! -z "$errors" ];then
+    local errors="$(echo "$output" | grep '^[(E)|(Err]:')"
+    if [ -z "$errors" ] && [ "$exitcode" != 0 ]; then
+      echo "User error: Apt exited with a failed exitcode ($exitcode) and no error (E/Err) output. This could indicate system corruption (eg: storage corruption or unstable overclocking)."
+      exit 1
+    elif [ ! -z "$errors" ];then
       echo -e "\e[91mFailed to install the packages!\e[39m"
-      echo -e "APT reported these errors:\n\e[91m$errors\e[39m"
-      echo "$output"
-
+      echo -e "The APT reported these errors:\n\e[91m$errors\e[39m"      
       #some error reports seem to indicate that package URLs aren't being properly downloaded. This output aims to solve the mystery.
       if [ "$using_local_packages" == 1 ] && [ ! -f /tmp/pi-apps-local-packages/Packages ];then
         echo "User error: Uh-oh, the /tmp/pi-apps-local-packages folder went missing while installing packages.\nThis usually happens if you try to install several apps at the same time in multiple terminals."