Check for the existence of all packages in yum before attempting install

Fixes clalancette#225

oz/RedHat.py

@@ -57,7 +57,7 @@ def __init__(self, tdl, config, auto, output_disk, nicmodel, diskbus,
 AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
 AcceptEnv XMODIFIERS
 X11Forwarding yes
-Subsystem	sftp	/usr/libexec/openssh/sftp-server
+Subsystem   sftp    /usr/libexec/openssh/sftp-server
 """
 
         # initrdtype is actually a tri-state:
@@ -816,6 +816,20 @@ def _customize_repos(self, guestaddr):
 
     def _install_packages(self, guestaddr, packstr):
         if self.use_yum:
+            # If passed in multiple packages, yum will still return a zero even if
+            # some of packages were not available for install. It seems the only
+            # safe way to check is to do a yum info on each package.
+            missing_packages = []
+            for package in packstr.split():
+                # Verify each package is available
+                try:
+                    self.guest_execute_command(guestaddr, 'yum info %s' % package)
+                except oz.ozutil.SubprocessException:
+                    missing_packages.append(package)
+            if missing_packages:
+                raise oz.OzException.OzException(
+                    'Failed to find packages: %s' % ' '.join(missing_packages)
+                )
             self.guest_execute_command(guestaddr, 'yum -y install %s' % (packstr))
         else:
             self.guest_execute_command(guestaddr, 'dnf -y install %s' % (packstr))