blivet 3.4.2

• pylint: Remove pdb breakpoint in device_properties_test (vtrefny)
• pylint: Fix exception string in get_cow_sysfs_path (vtrefny)
• pylint: Remove redundant 'u' prefixes for strings in doc/conf.py (vtrefny)
• pylint: Ignore the "redundant-u-string-prefix" warning in i18n.py (vtrefny)
• pylint: Ignore the new warning W1514 "unspecified-encoding" (vtrefny)
• pylint: Fix multuple unused variables 'e' in exceptions (vtrefny)
• Makefile: Specify weblate repository branch for the potfile target (vtrefny)
• flags: Fix leaking file descriptor (vtrefny)
• README: Add info about our openSUSE/Mageia/OpenMandriva Copr repo (vtrefny)
• Fix checking for LVM VDO support with libblockdev 2.23 and older (vtrefny)
• tasks: Allow specifying custom error message for UnavailableMethod (vtrefny)
• Use setuptools instead of distutils in setup.py (vtrefny)
• Use shutil.which instead of distutils.spawn.find_executable (vtrefny)
• Do not use FS.mount for btrfs temporary mounts (vtrefny)