Overhaul registry interface

CHANGES.rst

@@ -5,6 +5,12 @@
   for services like ESO's and MAST's TAP, which do not use canonical
   prefixes while astropy.utils.xml ignores namespaces. [#323]
 
+- Overhaul of the registry.regsearch as discussed in
+  https://blog.g-vo.org/towards-data-discovery-in-pyvo.html.  This
+  should be backwards-compatible. [#289]
+
+- Versions of astropy <4.1 are no longer supported. [#289]
+
 
 1.3.1 (unreleased)
 ==================

README.rst

@@ -50,7 +50,7 @@ PyVO requires Python 3.8 or later.
 
 The following packages are required for PyVO:
 
- * `astropy <https://astropy.org>`__ (>=4.0)
+ * `astropy <https://astropy.org>`__ (>=4.1)
  * `requests <http://docs.python-requests.org/en/latest/>`_
 
 The following packages are optional dependencies and are required for the

pyvo/registry/__init__.py

@@ -4,9 +4,12 @@
 
 The regtap module supports access to the IVOA Registries
 """
-from . import regtap
+from .regtap import search, ivoid2service, get_RegTAP_query
+
+from .rtcons import (Constraint, 
+    Freetext, Author, Servicetype, Waveband, Datamodel, Ivoid,
+    UCD, Spatial, Spectral, Temporal)
 
-search = regtap.search
-ivoid2service = regtap.ivoid2service
-
-__all__ = ["search"]
+__all__ = ["search", "get_RegTAP_query", "Freetext", "Author",
+    "Servicetype", "Waveband", "Datamodel", "Ivoid", "UCD",
+    "Spatial", "Spectral", "Temporal"]