Remove obsolete DM-Upload-Allowed flag
"if not" also triggers when value is 0, use "if is None" instead
Fix spelling.
Improve error handling.

In method unmount: If unmount impossible, write a message to logging
before it finally raises (fixes inconsistency with other error handling).

In method copy_bootloader_files: Provide an Exception instance to provide
an useful error message.
Wrap main method with try...except Exception construct.

This construct will catch any Exception and suppresses the backtrace.
Any error message is registered by logging before. In the current
commit this is already satisfied, but error message might get registered
twice.

Next we don't register error messages with logging before and move the
logging.critical message to the top-level except-Exception.
Provide top-level critical error message.

Instead of registering error message using the logging module before
raising the corresponding Exception, we use the Exception to provide
user-level error messages (and use logging.debug or logging.error to
store dev-level error messages before).

The main routine catches those exceptions and forwards the messages
to the logging module.
Fix typo.
Fix FORMAT definition for logging module.

Level does not specify that only messages of this level are printed
out, but the minimum level. So a definition like this

    FORMAT = "Debug: %(asctime)-15s %(message)s"
    FORMAT = "%(asctime)-15s %(message)s"

misleads the user into thinking that every message printed out is
actually a debug message, which is not true.
We now use "%(message)s" for everything except verbose mode which
annotates the timestamp to the message.
Bugfixes.

Several bugfixes concerning the error handling of the previous commits.
Further bugfixes.

* Remove "Error:" prefix which will be added as "Critical:" anyway.
* Fix wrong usage of string formatting parameters.
Release new version 0.13.7
Skip check for bootflag if a GPT header is present

The bootflag is not required when using GPT, so skip the check
and do not fail if no bootflag is present.
Release new version 0.13.8
grml2iso: skip --uefi option of isohybrid if ISO doesn't ship /boot/efi.img

Grml's 32bit ISOs don't provide /boot/efi.img, so there's no
point in running isohybrid with its --uefi option then as
this fails.
Use lowercase 'timeout' command in syslinux configuration [Closes: issue1262]

With an uppercase 'TIMEOUT' command the system seems to be failing
to autoboot for a user (using kernel version 3.9-1-amd64 on a
ThinkPad T410s). While syslinux shouldn't care about it
("Keywords are case insensitive") changing the uppercase command
to lowercase fixes the issue, so let's go for it.

Thanks: Martin Šlouf for reporting this bug including a workaround
grml2iso: extend error message of required ISO generation tools with xorriso
grml2iso: mention isolinux in 'isohybrid executable not found' message, add isolinux to recommends

Binary package syslinux in version 3:4.05+dfsg-6+deb7u3 ships the
isohybrid binary, but starting with version 3:6.00+dfsg-1 the
isohybrid binary is part of the isolinux binary package...
grml2iso: disable UEFI mode by default, only enable for xorriso under according prerequisites

Getting an error message like:

| isohybrid version supports --uefi option, enabling
| Creating dd-able ISO using isohybrid
| isohybrid: custom_grml.iso: unable to find efi image

is quite confusing, especially if the /efi/boot/bootx64.efi
and /boot/efi.img files are actually present on the image.

When using xorriso everything is fine, but when using genisoimage
within grml2iso the ISO lacks according UEFI support and the
above mention error message appears. So instead only enable UEFI
mode if building with xorriso and all the other prerequisites are
fulfilled as well.
grml2iso: make sure we have the sbin directories in our PATH

Under Debian/wheezy it fails out-of-the-box under sudo:

| sudo /usr/sbin/grml2iso -c ./source/templates -o grml64-sipwise-release_20130626.iso grml64-full_2013.02.iso
| Error: Could not find grml2usb executable. Is /usr/sbin missing in PATH?

because of:

| ENV_SUPATH      PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
| ENV_PATH        PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games

in /etc/login.defs.
Release new version 0.14.0