remove exists() call from glob and versioning, trying tocatch exceptions instead when possible

Signed-off-by: Timothée Peignier <timothee.peignier@tryphon.org>

pipeline/glob.py

@@ -23,7 +23,6 @@ def iglob(pathname):
 
     """
     if not has_magic(pathname):
-        if storage.exists(pathname):
         yield pathname
         return
     dirname, basename = os.path.split(pathname)

pipeline/versioning/__init__.py

@@ -39,8 +39,6 @@ class Versioning(object):
     def need_update(self, output_file, paths):
         version = self.version(paths)
         output_file = self.output_filename(output_file, version)
-        if not storage.exists(output_file):
-            return True, version
         return getattr(self.versioner, 'need_update')(output_file, paths, version)
 
     def cleanup(self, filename):

pipeline/versioning/mtime/__init__.py

@@ -13,4 +13,8 @@ class MTimeVersioning(VersioningBase):
 
     def need_update(self, output_file, paths, version):
         output_filename = self.output_filename(output_file, version)
-        return (int(time.mktime(storage.modified_time(output_filename).timetuple())) < int(version)), version
+        try:
+            modified_time = storage.modified_time(output_filename)
+        except EnvironmentError:
+            return True, version
+        return (int(time.mktime(modified_time.timetuple())) < int(version)), version