[packages] Feature: skip if no internet.

Update documentation, add a new key *skip_if_no_internet* to support
systems that **recommend** having an internet connection (but don't
require it), and which also use the packages module. This prevents
a long delay while the package manager tries to access the internet
and times out (repeatedly).

Existing configurations are unchanged.

src/modules/packages/main.py

@@ -426,6 +426,11 @@ def run():
     else:
         return "Bad backend", "backend=\"{}\"".format(backend)
 
+    skip_this = libcalamares.job.configuration.get("skip_if_no_internet", false)
+    if skip_this and not libcalamares.globalstorage.value("hasInternet"):
+        cDebug() << "WARNING: packages installation has been skipped: no internet";
+        return None
+
     update_db = libcalamares.job.configuration.get("update_db", False)
     if update_db and libcalamares.globalstorage.value("hasInternet"):
         pkgman.update_db()

src/modules/packages/packages.conf

@@ -14,9 +14,20 @@
 #
 backend: dummy
 
-# If set to true, a package-manager specific update procedure
-# is run first (only if there is internet) to update the list
-# of packages and dependencies.
+# Often package installation needs an internet connection.
+# Since you may allow system installation without a connection
+# and want to offer **optional** package installation, it's
+# possible to have no internet, yet have this packages module
+# enabled in settings.
+#
+# You can skip the whole module when there is no internet
+# by setting *skip_if_no_internet* to true.
+#
+# You can run a package-manager specific update procedure
+# before installing packages (for instance, to update the
+# list of packages and dependencies); this is done only if there
+# is an internet connection. Set *update_db* to true to do so.
+skip_if_no_internet: false
 update_db: true
 
 #