Inhibit upgrade if multiple kernel-devel pkgs are installed

When multiple kernel-devel packages are present, leapp can't process
the transaction in some cases, so we inhibit the upgrade and present
the user with hints on removing the surplus devel kernels.

repos/system_upgrade/el7toel8/actors/kernel/checkinstalleddevelkernels/actor.py

@@ -0,0 +1,23 @@
+from leapp.actors import Actor
+from leapp.models import InstalledRedHatSignedRPM
+from leapp.tags import IPUWorkflowTag, ChecksPhaseTag
+from leapp.reporting import Report
+from leapp.libraries.actor import library
+
+
+class CheckInstalledDevelKernels(Actor):
+    """
+    Inhibit IPU (in-place upgrade) when multiple devel kernels are installed.
+
+    Because of an issue in DNF, the transaction can't be validated if there's
+    more than one package named kernel-devel. Therefore, in this case, we
+    inhibit the upgrade with a clearer remediation.
+    """
+
+    name = 'check_installed_devel_kernels'
+    consumes = (InstalledRedHatSignedRPM,)
+    produces = (Report,)
+    tags = (IPUWorkflowTag, ChecksPhaseTag)
+
+    def process(self):
+        library.process()

repos/system_upgrade/el7toel8/actors/kernel/checkinstalleddevelkernels/libraries/library.py

@@ -0,0 +1,40 @@
+from leapp import reporting
+from leapp.libraries.stdlib import api
+from leapp.models import InstalledRedHatSignedRPM
+
+
+def get_kernel_rpm_release(rpm):
+    """
+    Get the release of a kernel RPM as an integer.
+
+    :param rpm: An instance of an RPM derived model.
+    """
+    return int(rpm.release.split('.')[0])
+
+
+def get_kernel_devel_rpms():
+    """
+    Get all installed kernel-devel packages ordered by release number (ascending).
+    """
+    rpms = next(api.consume(InstalledRedHatSignedRPM), InstalledRedHatSignedRPM())
+    return sorted([pkg for pkg in rpms.items if pkg.name == 'kernel-devel'], key=get_kernel_rpm_release)
+
+
+def process():
+    pkgs = get_kernel_devel_rpms()
+    if len(pkgs) > 1:
+        title = 'Multiple devel kernels installed'
+        summary = ('DNF cannot produce a valid upgrade transaction when'
+                   ' multiple kernel-devel packages are installed.')
+        hint = ('Remove all but one kernel-devel packages before running Leapp again.')
+        commands = ([['yum', '-y', 'remove', '{n}-{v}.{r}'.format(
+            n=pkg.name, v=pkg.version, r=pkg.release)] for pkg in pkgs[:-1]])
+        reporting.create_report([
+            reporting.Title(title),
+            reporting.Summary(summary),
+            reporting.Severity(reporting.Severity.HIGH),
+            reporting.Tags([reporting.Tags.KERNEL]),
+            reporting.Flags([reporting.Flags.INHIBITOR]),
+            reporting.Remediation(hint=hint, commands=commands),
+            reporting.RelatedResource('package', 'kernel')
+        ])

repos/system_upgrade/el7toel8/actors/kernel/checkinstalleddevelkernels/tests/unit_test.py

@@ -0,0 +1,36 @@
+import pytest
+
+from leapp.models import InstalledRedHatSignedRPM, RPM, Report
+from leapp.snactor.fixture import current_actor_context
+
+
+RH_PACKAGER = 'Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>'
+
+ballast1 = [
+    RPM(name='b1', version='1', release='1', epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s'),
+    RPM(name='kernel', version='1', release='1', epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s'),
+    RPM(name='b2', version='1', release='1', epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s')
+]
+ballast2 = [
+    RPM(name='b3', version='1', release='1', epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s'),
+    RPM(name='kernel', version='1', release='1', epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s'),
+    RPM(name='b4', version='1', release='1', epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s')
+]
+devel_kernels = [
+    RPM(name='kernel-devel', version='3.10.0', release='957.27.4.el7',
+        epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s'),
+    RPM(name='kernel-devel', version='3.10.0', release='957.35.1.el7',
+        epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s'),
+    RPM(name='kernel-devel', version='3.10.0', release='957.43.1.el7',
+        epoch='1', packager=RH_PACKAGER, arch='noarch', pgpsig='s')
+]
+
+
+@pytest.mark.parametrize('n', [0, 1, 2, 3])
+def test_process_devel_kernels(current_actor_context, n):
+    current_actor_context.feed(InstalledRedHatSignedRPM(items=ballast1+devel_kernels[:n]+ballast2))
+    current_actor_context.run()
+    if n < 2:
+        assert not current_actor_context.consume(Report)
+    else:
+        assert current_actor_context.consume(Report)