Adding a theano shim to point to pymc3 and emit deprecation warning

python/celerite2/theano/__init__.py

@@ -0,0 +1,12 @@
+__all__ = ["terms", "GaussianProcess"]
+
+import warnings
+
+warnings.warn(
+    "The `celerite2.theano` submodule is deprecated; "
+    "use `celerite2.pymc3` instead",
+    DeprecationWarning,
+)
+
+from celerite2.pymc3.celerite2 import GaussianProcess
+from celerite2.theano import terms

python/celerite2/theano/terms.py

@@ -0,0 +1,25 @@
+__all__ = [
+    "Term",
+    "TermSum",
+    "TermProduct",
+    "TermDiff",
+    "TermConvolution",
+    "RealTerm",
+    "ComplexTerm",
+    "SHOTerm",
+    "Matern32Term",
+    "RotationTerm",
+]
+
+from celerite2.pymc3.terms import (
+    ComplexTerm,
+    Matern32Term,
+    RealTerm,
+    RotationTerm,
+    SHOTerm,
+    Term,
+    TermConvolution,
+    TermDiff,
+    TermProduct,
+    TermSum,
+)

python/test/pymc3/test_pymc3_celerite2.py

@@ -29,6 +29,13 @@
 )
 
 
+def test_theano_import_warns():
+    with pytest.deprecated_call():
+        import celerite2.theano
+
+        del celerite2.theano
+
+
 @pytest.fixture
 def data():
     np.random.seed(40582)