better lxc-pack unlinking

zz-extra/lxc-pack

@@ -31,11 +31,10 @@ def pack(pkg_file):
     xz_path = '{}.xz'.format(tar_path)
 
     # Remove old package
-    try:
+    if os.path.exists(tar_path):
         os.unlink(tar_path)
+    if os.path.exists(xz_path):
         os.unlink(xz_path)
-    except:
-        pass
 
     # Create archive
     print('Archiving', meta['lxcpath'])
@@ -51,11 +50,9 @@ def pack(pkg_file):
     print('Registering package')
     packages = {}
     packages_file = os.path.join(BUILD_ROOT, 'packages')
-    try:
+    if os.path.exists(packages_file):
         with open(packages_file, 'r') as fd:
             packages = json.load(fd)
-    except:
-        pass
     packages[pkg_name] = meta
     with open(packages_file, 'w') as fd:
         json.dump(packages, fd, sort_keys=True, indent=4)