salt: close rpm DB & yum repo/cache

We forgot to close databases after checking the presence
of packages in repositories, it can lead to DB related errors
when trying to use yum just after calling the salt custom module

Refs: #1970

salt/_modules/metalk8s_package_manager_yum.py

@@ -4,6 +4,7 @@
 '''
 import logging
 
+from contextlib import contextmanager
 from salt.exceptions import CommandExecutionError
 
 try:
@@ -168,6 +169,16 @@ def _disable_yum_loggers():
         yum_logger.setLevel(yum.logginglevels.__NO_LOGGING)
 
 
+@contextmanager
+def _get_yum_base():
+    ybase = yum.YumBase()
+    try:
+        yield ybase
+    finally:
+        ybase.closeRpmDB()
+        ybase.close()
+
+
 def check_pkg_availability(pkgs_info):
     '''
     Check that provided packages and their dependencies are available
@@ -176,38 +187,39 @@ def check_pkg_availability(pkgs_info):
         Value of pillar key `repo:packages` to consider for the requiring
         packages to check (format {"<name>": {"version": "<version>"}, ...})
     '''
-    ybase = yum.YumBase()
-    ybase.preconf.errorlevel = 0
-    ybase.preconf.debuglevel = 0
-    ybase.conf.tsflags = 'test'
-    ybase.conf.assumeyes = True
+    with _get_yum_base() as ybase:
+        ybase.preconf.errorlevel = 0
+        ybase.preconf.debuglevel = 0
+        ybase.conf.tsflags = 'test'
+        ybase.conf.assumeyes = True
 
-    _disable_yum_loggers()
+        _disable_yum_loggers()
 
-    for name, info in pkgs_info.items():
+        for name, info in pkgs_info.items():
 
-        version = info.get('version')
-        release = None
+            version = info.get('version')
+            release = None
 
-        if version:
-            version_with_release = version.split('-', 1)
-            if len(version_with_release) == 2:
-                version = version_with_release[0]
-                release = version_with_release[1]
+            if version:
+                version_with_release = version.split('-', 1)
+                if len(version_with_release) == 2:
+                    version = version_with_release[0]
+                    release = version_with_release[1]
 
-        try:
-            ybase.install(name=name, version=version, release=release)
-        except yum.Errors.InstallError as exc:
-            error = 'No candidate found for package: {0}{1}'.format(
-                name, '-' + str(version) if version else ''
-            )
-            raise CommandExecutionError(error)
+            try:
+                ybase.install(name=name, version=version, release=release)
+            except yum.Errors.InstallError as exc:
+                error = 'No candidate found for package: {0}{1}'.format(
+                    name, '-' + str(version) if version else ''
+                )
+                raise CommandExecutionError(error)
 
-    ybase.resolveDeps()
-    ybase.buildTransaction()
+        ybase.resolveDeps()
+        ybase.buildTransaction()
 
-    try:
-        ybase.processTransaction()
-    except (yum.Errors.YumDownloadError, yum.Errors.YumRPMCheckError) as exc:
-        error = 'Some package dependencies are missing: {0}'.format(exc)
-        raise CommandExecutionError(error)
+        try:
+            ybase.processTransaction()
+        except (yum.Errors.YumDownloadError,
+                yum.Errors.YumRPMCheckError) as exc:
+            error = 'Some package dependencies are missing: {0}'.format(exc)
+            raise CommandExecutionError(error)