Fixed #23658 -- Provided the password to PostgreSQL dbshell command

The password from settings.py is written in a temporary .pgpass file
file whose name is given to psql using the PGPASSFILE environment
variable.

django/db/backends/postgresql_psycopg2/client.py

@@ -1,19 +1,66 @@
+import os
 import subprocess
 
+from django.core.files.temp import NamedTemporaryFile
 from django.db.backends.base.client import BaseDatabaseClient
+from django.utils.six import print_
+
+
+def _escape_pgpass(txt):
+    """
+    Escape a fragment of a PostgreSQL .pgpass file.
+    """
+    return txt.replace('\\', '\\\\').replace(':', '\\:')
 
 
 class DatabaseClient(BaseDatabaseClient):
     executable_name = 'psql'
 
+    @classmethod
+    def runshell_db(cls, settings_dict):
+        args = [cls.executable_name]
+
+        host = settings_dict.get('HOST', '')
+        port = settings_dict.get('PORT', '')
+        name = settings_dict.get('NAME', '')
+        user = settings_dict.get('USER', '')
+        passwd = settings_dict.get('PASSWORD', '')
+
+        if user:
+            args += ['-U', user]
+        if host:
+            args += ['-h', host]
+        if port:
+            args += ['-p', str(port)]
+        args += [name]
+
+        temp_pgpass = None
+        try:
+            if passwd:
+                # Create temporary .pgpass file.
+                temp_pgpass = NamedTemporaryFile(mode='w+')
+                try:
+                    print_(
+                        _escape_pgpass(host) or '*',
+                        str(port) or '*',
+                        _escape_pgpass(name) or '*',
+                        _escape_pgpass(user) or '*',
+                        _escape_pgpass(passwd),
+                        file=temp_pgpass,
+                        sep=':',
+                        flush=True,
+                    )
+                    os.environ['PGPASSFILE'] = temp_pgpass.name
+                except UnicodeEncodeError:
+                    # If the current locale can't encode the data, we let
+                    # the user input the password manually.
+                    pass
+            subprocess.call(args)
+        finally:
+            if temp_pgpass:
+                temp_pgpass.close()
+                if 'PGPASSFILE' in os.environ:  # unit tests need cleanup
+                    del os.environ['PGPASSFILE']
+
     def runshell(self):
-        settings_dict = self.connection.settings_dict
-        args = [self.executable_name]
-        if settings_dict['USER']:
-            args += ["-U", settings_dict['USER']]
-        if settings_dict['HOST']:
-            args.extend(["-h", settings_dict['HOST']])
-        if settings_dict['PORT']:
-            args.extend(["-p", str(settings_dict['PORT'])])
-        args += [settings_dict['NAME']]
-        subprocess.call(args)
+        DatabaseClient.runshell_db(self.connection.settings_dict)