loadelement.py: Switch from roaringbitmap to pyroaring

The licence for roaringbitmap was not compatible.  pyroaring is
a similar project which is MIT licensed and is slightly better on
memory too.

Signed-off-by: Daniel Silverstone <daniel.silverstone@codethink.co.uk>

buildstream/_loader/loadelement.py

@@ -21,7 +21,7 @@
 from collections.abc import Mapping
 from itertools import count
 
-from roaringbitmap import RoaringBitmap, ImmutableRoaringBitmap  # pylint: disable=no-name-in-module
+from pyroaring import BitMap, FrozenBitMap  # pylint: disable=no-name-in-module
 
 # BuildStream toplevel imports
 from .._exceptions import LoadError, LoadErrorReason
@@ -123,7 +123,7 @@ class LoadElement():
         if self._dep_cache:
             return
 
-        self._dep_cache = RoaringBitmap()
+        self._dep_cache = BitMap()
 
         for dep in self.dependencies:
             elt = dep.element
@@ -137,7 +137,7 @@ class LoadElement():
             # And we depend on everything this element depends on
             self._dep_cache.update(elt._dep_cache)
 
-        self._dep_cache = ImmutableRoaringBitmap(self._dep_cache)
+        self._dep_cache = FrozenBitMap(self._dep_cache)
 
 
 # _extract_depends_from_node():

requirements/requirements.in

@@ -13,6 +13,4 @@ psutil
 # See issues #571 and #790.
 ruamel.yaml >= 0.15.41, < 0.15.52
 setuptools
-# (Potentially) short-term need for roaring bitmaps for the
-# loader dependency sorting
-roaringbitmap
+pyroaring

requirements/requirements.txt

@@ -13,9 +13,7 @@ psutil==5.4.8
 # See issues #571 and #790.
 ruamel.yaml==0.15.51
 setuptools==39.0.1
-# (Potentially) short-term need for roaring bitmaps for the
-# loader dependency sorting
-roaringbitmap==0.6
+pyroaring==0.2.6
 ## The following requirements were added by pip freeze:
 MarkupSafe==1.1.0
 six==1.12.0