Allow double close in sqlite backend (#3148)

pymc3/backends/sqlite.py

@@ -113,12 +113,13 @@ def setup(self, draws, chain):
             self._create_table()
             self._is_setup = True
         self._create_insert_queries()
+        self._closed = False
 
     def _create_table(self):
         template = TEMPLATES['table']
         with self.db.con:
             for varname, var_cols in self._var_cols.items():
-                if np.issubdtype(self.var_dtypes[varname], np.int):
+                if np.issubdtype(self.var_dtypes[varname], np.integer):
                     dtype = 'INT'
                 else:
                     dtype = 'FLOAT'
@@ -164,8 +165,11 @@ def _execute_queue(self):
                 self._queue[varname] = []
 
     def close(self):
+        if self._closed:
+            return
         self._execute_queue()
         self.db.close()
+        self._closed = True
 
     # Selection methods
 

pymc3/tests/backend_fixtures.py

@@ -60,6 +60,10 @@ def test_append(self):
             self.strace.setup(self.draws, self.chain, self.sampler_vars)
             assert len(self.strace) == 0
 
+    def test_double_close(self):
+        self.strace.close()
+        self.strace.close()
+
     def teardown_method(self):
         if self.name is not None:
             remove_file_or_directory(self.name)