fix: Fix 'possibly-used-before-assignment' pylint issues

Latest pylint added a new check for values used before assignment.
This fixes these issues found in the blivet module. Some of these
are false positives, some real potential issues.

library/blivet.py

@@ -642,6 +642,8 @@ def _look_up_device(self):
             self._device = None
             return  # TODO: see if we can create this device w/ the specified name
 
+    # pylint doesn't understand that "luks_fmt" is always set when "encrypted" is true
+    # pylint: disable=possibly-used-before-assignment
     def _update_from_device(self, param_name):
         """ Return True if param_name's value was retrieved from a looked-up device. """
         log.debug("Updating volume settings from device: %r", self._device)
@@ -1717,6 +1719,8 @@ def str_to_size(spec, hundredpercent=None):
 
         if auto_size_dev_count > 0:
             calculated_thinlv_size = available_space / auto_size_dev_count
+        else:
+            calculated_thinlv_size = available_space
 
         for thinlv in thinlvs_to_create:
 

pylintrc

@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: MIT
 
-# This file was generated using `pylint --generate-rcfile > pylintrc` command. 
+# This file was generated using `pylint --generate-rcfile > pylintrc` command.
 [MASTER]
 
 # A comma-separated list of package or module names from where C extensions may
@@ -57,7 +57,8 @@ confidence=
 # --enable=similarities". If you want to run only the classes checker, but have
 # no Warning level messages displayed, use"--disable=all --enable=classes
 # --disable=W"
-disable=wrong-import-position
+disable=wrong-import-position,
+        unknown-option-value
 #disable=print-statement,
 #        parameter-unpacking,
 #        unpacking-in-except,