[mount] Print a warning if mount failure

The return of the call to libcalamares.utils.mount is never tested and
it may fail silently; this causes some mounpoints to be missing.

This adds a warning if mountpoint cannot be mounted.

	chcon: failed to get security context of '/tmp/verity': Operation not supported
	06:44:23 [6]: static CalamaresUtils::ProcessResult CalamaresUtils::System::runCommand(CalamaresUtils::System::RunLocation, const QStringList&, const QString&, const QString&, std::chrono::seconds)
	    Running "env" ("mount", "-t", "unformatted", "/dev/sdb2", "/tmp/calamares-root-kv8dqgb5/tmp/verity")
	    ..  Finished. Exit code: 32
	    ..  Target cmd: ("mount", "-t", "unformatted", "/dev/sdb7", "/tmp/calamares-root-kv8dqgb5/tmp/verity") output:
	 mount: /tmp/calamares-root-kv8dqgb5/tmp/verity: unknown filesystem type 'unformatted'.

src/modules/mount/main.py

@@ -7,6 +7,7 @@
 #   SPDX-FileCopyrightText: 2017 Alf Gaida <agaida@siduction.org>
 #   SPDX-FileCopyrightText: 2019 Adriaan de Groot <groot@kde.org>
 #   SPDX-FileCopyrightText: 2019 Kevin Kofler <kevin.kofler@chello.at>
+#   SPDX-FileCopyrightText: 2019-2020 Collabora Ltd
 #   SPDX-License-Identifier: GPL-3.0-or-later
 #
 #   Calamares is Free Software: see the License-Identifier above.
@@ -56,22 +57,16 @@ def mount_partition(root_mount_point, partition, partitions):
     if fstype == "fat16" or fstype == "fat32":
         fstype = "vfat"
 
+    device = partition["device"]
+
     if "luksMapperName" in partition:
-        libcalamares.utils.debug(
-            "about to mount {!s}".format(partition["luksMapperName"]))
-        libcalamares.utils.mount(
-            "/dev/mapper/{!s}".format(partition["luksMapperName"]),
-            mount_point,
-            fstype,
-            partition.get("options", ""),
-            )
-
-    else:
-        libcalamares.utils.mount(partition["device"],
-                                 mount_point,
-                                 fstype,
-                                 partition.get("options", ""),
-                                 )
+        device = os.path.join("/dev/mapper", partition["luksMapperName"])
+
+    if libcalamares.utils.mount(device,
+                                mount_point,
+                                fstype,
+                                partition.get("options", "")) != 0:
+        libcalamares.utils.warning("Cannot mount {}".format(device))
 
     # If the root partition is btrfs, we create a subvolume "@"
     # for the root mount point.
@@ -96,37 +91,23 @@ def mount_partition(root_mount_point, partition, partitions):
 
         subprocess.check_call(["umount", "-v", root_mount_point])
 
+        device = partition["device"]
+
         if "luksMapperName" in partition:
-            libcalamares.utils.mount(
-                "/dev/mapper/{!s}".format(partition["luksMapperName"]),
-                mount_point,
-                fstype,
-                ",".join(
-                    ["subvol=@", partition.get("options", "")]),
-                )
-            if not has_home_mount_point:
-                libcalamares.utils.mount(
-                    "/dev/mapper/{!s}".format(partition["luksMapperName"]),
-                    root_mount_point + "/home",
-                    fstype,
-                    ",".join(
-                        ["subvol=@home", partition.get("options", "")]),
-                    )
-        else:
-            libcalamares.utils.mount(
-                partition["device"],
-                mount_point,
-                fstype,
-                ",".join(["subvol=@", partition.get("options", "")]),
-                )
-            if not has_home_mount_point:
-                libcalamares.utils.mount(
-                    partition["device"],
-                    root_mount_point + "/home",
-                    fstype,
-                    ",".join(
-                        ["subvol=@home", partition.get("options", "")]),
-                    )
+            device = os.path.join("/dev/mapper", partition["luksMapperName"])
+
+        if libcalamares.utils.mount(device,
+                                    mount_point,
+                                    fstype,
+                                    ",".join(["subvol=@", partition.get("options", "")])) != 0:
+            libcalamares.utils.warning("Cannot mount {}".format(device))
+
+        if not has_home_mount_point:
+            if libcalamares.utils.mount(device,
+                                        root_mount_point + "/home",
+                                        fstype,
+                                        ",".join(["subvol=@home", partition.get("options", "")])) != 0:
+                libcalamares.utils.warning("Cannot mount {}".format(device))
 
 
 def run():