Remove superfluous try-except from meter import

Since commit 8a6abe3a6c ("warn user
if python-progressbar is not installed") it is always safe to import
the meter module (even if the progressbar module is not installed).

osc/fetch.py

@@ -23,10 +23,7 @@ from . import oscerr
 import tempfile
 import re
 
-try:
-    from .meter import TextMeter
-except ImportError:
-    TextMeter = None
+from .meter import TextMeter
 
 
 class Fetcher: