Try to track the capabilities of our outputdir filesystem.

For example, don't chmod if the filesystem dosen't support chmod, and
don't rename over files if that's not supported (this functionality was
already in place).

Should fix #1061
Related to #1055 (we could add a mtime capability flag)

overviewer_core/tileset.py

@@ -31,7 +31,7 @@ from PIL import Image
 
 from .util import roundrobin
 from . import nbt
-from .files import FileReplacer
+from .files import FileReplacer, get_fs_caps
 from .optimizeimages import optimize_image
 import rendermodes
 import c_overviewer
@@ -357,6 +357,9 @@ class TileSet(object):
                 self.options['renderchecks'] = 2
             os.mkdir(self.outputdir)
 
+        # must wait until outputdir exists
+        self.fs_caps = get_fs_caps(self.outputdir)
+
         if self.options['renderchecks'] == 2:
             # Set forcerendertime so that upon an interruption the next render
             # will continue where we left off.
@@ -902,7 +905,7 @@ class TileSet(object):
                     logging.error("While attempting to delete corrupt image %s, an error was encountered. You will need to delete it yourself. Error was '%s'", path[1], e)
 
         # Save it
-        with FileReplacer(imgpath) as tmppath:
+        with FileReplacer(imgpath, capabilities=self.fs_caps) as tmppath:
             if imgformat == 'jpg':
                 img.save(tmppath, "jpeg", quality=self.options['imgquality'], subsampling=0)
             else: # png
@@ -1006,7 +1009,7 @@ class TileSet(object):
             #draw.text((96,96), "c,r: %s,%s" % (col, row), fill='red')
 
         # Save them
-        with FileReplacer(imgpath) as tmppath:
+        with FileReplacer(imgpath, capabilities=self.fs_caps) as tmppath:
             if self.imgextension == 'jpg':
                 tileimg.save(tmppath, "jpeg", quality=self.options['imgquality'], subsampling=0)
             else: # png