Fix: Unable to drop previously connected-to database (#1152)

* close connections + added to authors + changelog

* check conn exists

AUTHORS

@@ -105,6 +105,7 @@ Contributors:
     * BrownShibaDog
     * George Thomas(thegeorgeous)
     * Yoni Nakache(lazydba247)
+    * Gantsev Denis
 
 Creator:
 --------

changelog.rst

@@ -11,6 +11,7 @@ Features:
 Bug fixes:
 
 * Fix warning raised for using `is not` to compare string literal
+* Close open connection in completion_refresher thread
 
 Internal:
 ---------

pgcli/completion_refresher.py

@@ -84,6 +84,10 @@ class CompletionRefresher(object):
         for callback in callbacks:
             callback(completer)
 
+        if not settings.get("single_connection") and executor.conn:
+            # close connection established with pgexecute.copy()
+            executor.conn.close()
+
 
 def refresher(name, refreshers=CompletionRefresher.refreshers):
     """Decorator to populate the dictionary of refreshers with the current