fix: don't fail the build when SQLite3 apt install fails

apt-get update fails because apt.postgresql.org dropped the xenial-pgdg
repo (404), which under set -e silently killed every build. Skip SQLite3
gracefully instead; python runtimes ship the sqlite3 module already and
apps on this stack use postgres.

bin/steps/sqlite3

@@ -31,11 +31,11 @@ sqlite3_install() {
   APT_OPTIONS="$APT_OPTIONS -o dir::state=$APT_STATE_DIR"
   APT_OPTIONS="$APT_OPTIONS -o dir::etc::sourcelist=/etc/apt/sources.list"
 
-  apt-get $APT_OPTIONS update > /dev/null 2>&1
+  apt-get $APT_OPTIONS update > /dev/null 2>&1 || return 1
   if [ -z "$HEADERS_ONLY" ]; then
-    apt-get $APT_OPTIONS -y -d --reinstall install libsqlite3-dev="$SQLITE3_VERSION" sqlite3="$SQLITE3_VERSION" > /dev/null 2>&1
+    apt-get $APT_OPTIONS -y -d --reinstall install libsqlite3-dev="$SQLITE3_VERSION" sqlite3="$SQLITE3_VERSION" > /dev/null 2>&1 || return 1
   else
-    apt-get $APT_OPTIONS -y -d --reinstall install libsqlite3-dev="$SQLITE3_VERSION"
+    apt-get $APT_OPTIONS -y -d --reinstall install libsqlite3-dev="$SQLITE3_VERSION" > /dev/null 2>&1 || return 1
   fi
 
   find "$APT_CACHE_DIR/archives/" -name "*.deb" -exec dpkg -x {} "$HEROKU_PYTHON_DIR/sqlite3/" \;
@@ -81,11 +81,13 @@ buildpack_sqlite3_install() {
     # only install if the sqlite3 version has changed
     if [ "$INSTALLED_SQLITE3_VERSION" != "$SQLITE3_VERSION" ]; then
       puts-step "Installing SQLite3"
-      sqlite3_install "$BUILD_DIR/.heroku/python" "$SQLITE3_VERSION"
-
-      # save version installed
-      mkdir -p "$CACHE_DIR/.heroku/"
-      echo "$SQLITE3_VERSION" > "$CACHE_DIR/.heroku/python-sqlite3-version"
+      if sqlite3_install "$BUILD_DIR/.heroku/python" "$SQLITE3_VERSION"; then
+        # save version installed
+        mkdir -p "$CACHE_DIR/.heroku/"
+        echo "$SQLITE3_VERSION" > "$CACHE_DIR/.heroku/python-sqlite3-version"
+      else
+        puts-warn "SQLite3 install failed (EOL apt repos?), continuing without it"
+      fi
     fi
   fi
 }