sanity.bbclass: Increased verbosity for connectivity check

The connectivity sanity error doesn't tell you which URL failed to fetch nor how
it failed.

This provides the URL that failed and why it failed using BBFetchException
messages during the connectivity check.

[YOCTO #7592]

(From OE-Core rev: e025d1ff02795fc9236b41606e916749f0d5e959)

Signed-off-by: Mariano Lopez <mariano.lopez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/sanity.bbclass

@@ -278,12 +278,12 @@ def check_connectivity(d):
         try:
             fetcher = bb.fetch2.Fetch(test_uris, data)
             fetcher.checkstatus()
-        except Exception:
+        except Exception as err:
             # Allow the message to be configured so that users can be
             # pointed to a support mechanism.
             msg = data.getVar('CONNECTIVITY_CHECK_MSG', True) or ""
             if len(msg) == 0:
-                msg = "Failed to fetch test data from the network. Please ensure your network is configured correctly.\n"
+                msg = "%s. Please ensure your network is configured correctly.\n" % err
             retval = msg
 
     return retval