core: use `bp` instead of `boost::python`

include/eigenpy/std-vector.hpp

@@ -419,16 +419,15 @@ struct StdVectorPythonVisitor {
   }
 
   template <typename DerivedVisitor>
-  static void expose(
-      const std::string &class_name,
-      const boost::python::def_visitor<DerivedVisitor> &visitor) {
+  static void expose(const std::string &class_name,
+                     const bp::def_visitor<DerivedVisitor> &visitor) {
     expose(class_name, "", visitor);
   }
 
   template <typename DerivedVisitor>
-  static void expose(
-      const std::string &class_name, const std::string &doc_string,
-      const boost::python::def_visitor<DerivedVisitor> &visitor) {
+  static void expose(const std::string &class_name,
+                     const std::string &doc_string,
+                     const bp::def_visitor<DerivedVisitor> &visitor) {
     // Apply visitor on already registered type or if type is not already
     // registered, we define and apply the visitor on it
     auto add_std_visitor =