New run_sanity_checks mechanism, for SpatiLite

Moved VirtualSpatialIndex check into a new mechanism that should allow
us to add further sanity checks in the future.

To test this I've had to commit a binary sample SpatiaLite database to
the repository. I included a build script for creating that database.

Closes #466

tests/build_small_spatialite_db.py

@@ -0,0 +1,23 @@
+import sqlite3
+
+# This script generates the spatialite.db file in our tests directory.
+
+
+def generate_it(filename):
+    conn = sqlite3.connect(filename)
+    # Lead the spatialite extension:
+    conn.enable_load_extension(True)
+    conn.load_extension("/usr/local/lib/mod_spatialite.dylib")
+    conn.execute("select InitSpatialMetadata(1)")
+    conn.executescript("create table museums (name text)")
+    conn.execute("SELECT AddGeometryColumn('museums', 'point_geom', 4326, 'POINT', 2);")
+    # At this point it is around 5MB - we can shrink it dramatically by doing thisO
+    conn.execute("delete from spatial_ref_sys")
+    conn.execute("delete from spatial_ref_sys_aux")
+    conn.commit()
+    conn.execute("vacuum")
+    conn.close()
+
+
+if __name__ == "__main__":
+    generate_it("spatialite.db")

tests/test_cli.py

@@ -1,6 +1,7 @@
 from .fixtures import app_client
 from datasette.cli import cli
 from click.testing import CliRunner
+import pathlib
 import json
 
 
@@ -28,3 +29,12 @@ def test_inspect_cli_writes_to_file(app_client):
     assert 0 == result.exit_code, result.output
     data = json.load(open("foo.json"))
     assert ["fixtures"] == list(data.keys())
+
+
+def test_spatialite_error_if_attempt_to_open_spatialite():
+    runner = CliRunner()
+    result = runner.invoke(
+        cli, ["serve", str(pathlib.Path(__file__).parent / "spatialite.db")]
+    )
+    assert result.exit_code != 0
+    assert "trying to load a SpatiaLite database" in result.output