[bzr-svn/merge] Don't overwrite bzrlib.errors.BzrError if sqlite3 is not available

[John Arbash Meinel]

I'm guessing this wasn't caught because Jelmer works mostly on 
python2.5. But in python2.4 the 'sqlite3' package isn't built-in. So 
this code has a problem:

=== modified file 'cache.py'
--- cache.py    2007-05-20 21:31:44 +0000
+++ cache.py    2007-05-21 16:33:53 +0000
@@ -52,7 +52,7 @@
      try:
          import sqlite3
          check_pysqlite_version(sqlite3)
-    except ImportError, bzrlib.errors.BzrError:
+    except ImportError, e:
          from pysqlite2 import dbapi2 as sqlite3
          check_pysqlite_version(sqlite3)
  except:

Basically, the way it is written, if the import fails, it assigns the 
ImportError object to bzrlib.errors.BzrError.

Which causes *lots* of very strange problems. Because we use 
BzrError.__init__(), rather than super(). And we don't use super() 
because python2.4 Exception objects are not new-style classes.

Anyway, the above patch makes things work correctly for me. I suppose if 
you really were worried about the other error you could make it:

except (ImportError, bzrlib.errors.BzrError), e:

John
=:->