fix(vrtManager): an architecture the host does not run is refused, not a 500

The create page and the API's create take the architecture from the
URL. One the host's capabilities do not list raised a KeyError in
get_dom_cap_xml: an HTML 500 for both. It is now "This host has no
architecture noarch": the page shows it, the API answers 400.

vrtManager/connection.py

@@ -497,7 +497,10 @@ class wvmConnect(object):
     def get_dom_cap_xml(self, arch, machine):
         """ Return domain capabilities xml"""
         emulatorbin = self.get_emulator(arch)
-        virttype = "kvm" if "kvm" in self.get_hypervisors_domain_types()[arch] else "qemu"
+        domain_types = self.get_hypervisors_domain_types().get(arch)
+        if domain_types is None:  # the architecture comes from the URL
+            raise util.OperationError(gettext_noop("This host has no architecture %(arch)s"), arch=arch)
+        virttype = "kvm" if "kvm" in domain_types else "qemu"
 
         machine_types = self.get_machine_types(arch)
         if not machine or machine not in machine_types:

vrtManager/tests/test_host_reads.py

@@ -20,6 +20,7 @@ from libvirt import (
     VIR_ERR_XML_ERROR,
     libvirtError,
 )
+from vrtManager import util
 from vrtManager.connection import wvmConnect
 from vrtManager.hostdetails import wvmHostDetails
 from vrtManager.storage import wvmStorage, wvmStorages
@@ -90,6 +91,11 @@ class CapabilitiesOnceTestCase(unittest.TestCase):
             ["capabilities", ("/usr/bin/qemu-kvm", "x86_64", "q35", "kvm"), ("/usr/bin/qemu-kvm", "x86_64", "pc", "kvm")],
         )
 
+    def test_an_architecture_the_host_does_not_run_is_refused_with_its_name(self):
+        # the create page and the API take it from the URL: it was a KeyError, a 500
+        with self.assertRaisesRegex(util.OperationError, "This host has no architecture noarch"):
+            connection().get_dom_cap_xml("noarch", "q35")
+
     def test_the_overview_reads_the_info_once_and_the_free_memory_each_time(self):
         conn = connection(wvmHostDetails)
         conn.get_node_info()