Remove imports of unicode_literals

I had put some of these in place to try and inch towards python3
somewhat. But people argue this isn't actually a good strategy:
PythonCharmers/python-future#22

idb/helpers/memoize.py

@@ -1,5 +1,5 @@
 from __future__ import division, absolute_import
-from __future__ import print_function, unicode_literals
+from __future__ import print_function
 
 from functools import wraps
 

idb/tests/test_helpers_media_validation.py

@@ -1,5 +1,5 @@
 from __future__ import division, absolute_import
-from __future__ import print_function, unicode_literals
+from __future__ import print_function
 
 import pytest
 
@@ -8,8 +8,8 @@
 
 def test_sniff_validation_jpg(jpgpath):
     mime, mtype = medval.sniff_validation(jpgpath.open('rb').read(1024))
-    assert mime == 'image/jpeg'
-    assert mtype == 'images'
+    assert mime == u'image/jpeg'
+    assert mtype == u'images'
 
 
 def test_sniff_validation_png(pngpath):
@@ -19,5 +19,5 @@ def test_sniff_validation_png(pngpath):
 
 def test_sniff_validation_mp3(mp3path):
     mime, mtype = medval.sniff_validation(mp3path.open('rb').read(1024))
-    assert mime == 'audio/mpeg'
-    assert mtype == 'sounds'
+    assert mime == u'audio/mpeg'
+    assert mtype == u'sounds'

idigbio_ingestion/derivatives.py

@@ -1,5 +1,5 @@
 from __future__ import division, absolute_import
-from __future__ import print_function, unicode_literals
+from __future__ import print_function
 from future_builtins import map, filter
 
 import os
@@ -84,8 +84,8 @@ def count_results(results, update_freq=100):
 def get_keys(obj):
     etag, bucket = obj.etag, obj.bucket
     s = IDigBioStorage()
-    bucketbase = "idigbio-{0}-{1}".format(bucket, ENV)
-    return CheckItem(etag, bucket,
+    bucketbase = u"idigbio-{0}-{1}".format(bucket, ENV)
+    return CheckItem(unicode(etag), bucket,
                      s.get_key(etag, bucketbase),
                      s.get_key(etag + ".jpg", bucketbase + "-thumbnail"),
                      s.get_key(etag + ".jpg", bucketbase + "-fullsize"),

idigbio_ingestion/verify_ceph_objects.py

@@ -4,7 +4,7 @@
 https://www.idigbio.org/redmine/issues/1863
 """
 from __future__ import division, absolute_import
-from __future__ import print_function, unicode_literals
+from __future__ import print_function
 
 import io
 import logging