[Dataset] Move file from dropbox to s3 (and fix ci fail due to sst dataset) (#205)

* move file from dropbox to s3

* fix ci and move sst to s3

* remove blank line

python/dgl/data/citation_graph.py

+
 """Cora, citeseer, pubmed dataset.
 
 (lingfan): following dataset loading and preprocessing code from tkipf/gcn
@@ -14,9 +15,9 @@ import os, sys
 from .utils import download, extract_archive, get_download_dir
 
 _urls = {
-    'cora' : 'https://www.dropbox.com/s/3ggdpkj7ou8svoc/cora.zip?dl=1',
-    'citeseer' : 'https://www.dropbox.com/s/cr4m05shgp8advz/citeseer.zip?dl=1',
-    'pubmed' : 'https://www.dropbox.com/s/fj5q6pi66xhymcm/pubmed.zip?dl=1',
+    'cora' : 'https://s3.amazonaws.com/dgl-data/dataset/cora.zip',
+    'citeseer' : 'https://s3.amazonaws.com/dgl-data/dataset/citeseer.zip',
+    'pubmed' : 'https://s3.amazonaws.com/dgl-data/dataset/pubmed.zip',
 }
 
 class CitationGraphDataset(object):

python/dgl/data/tree.py

@@ -17,7 +17,7 @@ import dgl.backend as F
 from dgl.data.utils import download, extract_archive, get_download_dir
 
 _urls = {
-    'sst': 'https://www.dropbox.com/s/aqejdgrs3jkrmc7/sst.zip?dl=1',
+    'sst' : 'https://s3.amazonaws.com/dgl-data/dataset/sst.zip',
 }
 
 SSTBatch = namedtuple('SSTBatch', ['graph', 'mask', 'wordid', 'label'])