Trap exception when trying to write csr

Trap the exception when trying to write the csr fails.
Fixes LP: #1092016

Change-Id: I05675c8c7b1d205a06d13dd3e62e06088d1b896d
Signed-off-by: Chuck Short <chuck.short@canonical.com>

nova/crypto.py

@@ -295,8 +295,12 @@ def _sign_csr(csr_text, ca_folder):
         inbound = os.path.join(tmpdir, 'inbound.csr')
         outbound = os.path.join(tmpdir, 'outbound.csr')
 
-        with open(inbound, 'w') as csrfile:
-            csrfile.write(csr_text)
+        try:
+            with open(inbound, 'w') as csrfile:
+                csrfile.write(csr_text)
+        except IOError:
+            LOG.exception(_('Failed to write inbound.csr'))
+            raise
 
         LOG.debug(_('Flags path: %s'), ca_folder)
         start = os.getcwd()