RPM: workaround timezone bug in spec parsing

The RPM library change the timezone when parsing spec file but old
versions of this library (<4.19) miss to restore the timezone properly.
This has the side effect to change the timezone for the end of Rift
execution, which could lead to weird behavior when parsing or
manipulating dates and times. In order to workaround this, Rift now
saves and restores the timezone itself, just to make sure everything is
in order after parsing the spec file.

Author: rezib

lib/rift/RPM.py

@@ -40,6 +40,7 @@
 import shutil
 from subprocess import Popen, PIPE, STDOUT, run, CalledProcessError
 import time
+import datetime
 
 import rpm
 
@@ -261,7 +262,16 @@ def load(self):
         try:
             rpm.reloadConfig()
             self._set_macros()
+            # Get current timezone, so it can be restored after parsing the spec
+            # file.
+            current_timezone = str(datetime.datetime.now(datetime.timezone.utc).astimezone().tzinfo)
             spec = rpm.TransactionSet().parseSpec(self.filepath)
+            # As a workaround RPM library bug
+            # https://github.com/rpm-software-management/rpm/issues/1821,
+            # restore timezone after it has been changed to parse changelog.
+            # Note this is fixed in RPM >= 4.19.
+            os.environ['TZ'] = str(current_timezone)
+            time.tzset()
         except ValueError as exp:
             raise RiftError(f"{self.filepath}: {exp}") from exp
         self.pkgnames = [_header_values(pkg.header['name']) for pkg in spec.packages]