Added guard to avoid importing psycog3_c without psycopg3

Doing so result in mysterious import error.

diff --git a/psycopg3_c/psycopg3_c/__init__.py b/psycopg3_c/psycopg3_c/__init__.py
index 8ab3af86f8c898e19b140a73f8e3c2ce23c78e5b..9093563a790ba669f20901e6ed36a68511b4a45c 100644 (file)
--- a/psycopg3_c/psycopg3_c/__init__.py
+++ b/psycopg3_c/psycopg3_c/__init__.py
@@ -4,4 +4,13 @@ psycopg3 -- PostgreSQL database adapter for Python -- C optimization package
 
 # Copyright (C) 2020 The Psycopg Team
 
+import sys
+
+# This package shouldn't be imported before psycopg3 itself, or weird things
+# will happen
+if "psycopg3" not in sys.modules:
+    raise ImportError(
+        "the psycopg3 package should be imported before psycopg3_c"
+    )
+
 from .version import __version__  # noqa