Import @dschep's module for installing postgres extensions.

Reviewed by @bcoca as a PR against the core repo here:
https://github.com/ansible/ansible-modules-core/pull/21

database/postgresql/postgresql_ext.py

@@ -0,0 +1,188 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+# This file is part of Ansible
+#
+# Ansible is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# Ansible is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.
+
+DOCUMENTATION = '''
+---
+module: postgresql_ext
+short_description: Add or remove PostgreSQL extensions from a database.
+description:
+   - Add or remove PostgreSQL extensions from a database.
+version_added: "0.1"
+options:
+  name:
+    description:
+      - name of the extension to add or remove
+    required: true
+    default: null
+  db:
+    description:
+      - name of the database to add or remove the extension to/from
+    required: true
+    default: null
+  login_user:
+    description:
+      - The username used to authenticate with
+    required: false
+    default: null
+  login_password:
+    description:
+      - The password used to authenticate with
+    required: false
+    default: null
+  login_host:
+    description:
+      - Host running the database
+    required: false
+    default: localhost
+  port:
+    description:
+      - Database port to connect to.
+    required: false
+    default: 5432
+   state:
+    description:
+      - The database extension state
+    required: false
+    default: present
+    choices: [ "present", "absent" ]
+notes:
+   - The default authentication assumes that you are either logging in as or sudo'ing to the C(postgres) account on the host.
+   - This module uses I(psycopg2), a Python PostgreSQL database adapter. You must ensure that psycopg2 is installed on
+     the host before using this module. If the remote host is the PostgreSQL server (which is the default case), then PostgreSQL must also be installed on the remote host. For Ubuntu-based systems, install the C(postgresql), C(libpq-dev), and C(python-psycopg2) packages on the remote host before using this module.
+requirements: [ psycopg2 ]
+author: Daniel Schep
+'''
+
+EXAMPLES = '''
+# Adds postgis to the database "acme"
+- postgresql_ext: name=postgis db=acme
+'''
+
+try:
+    import psycopg2
+    import psycopg2.extras
+except ImportError:
+    postgresqldb_found = False
+else:
+    postgresqldb_found = True
+
+class NotSupportedError(Exception):
+    pass
+
+
+# ===========================================
+# PostgreSQL module specific support methods.
+#
+
+def ext_exists(cursor, ext):
+    query = "SELECT * FROM pg_extension WHERE extname=%(ext)s"
+    cursor.execute(query, {'ext': ext})
+    return cursor.rowcount == 1
+
+def ext_delete(cursor, ext):
+    if ext_exists(cursor, ext):
+        query = "DROP EXTENSION \"%s\"" % ext
+        cursor.execute(query)
+        return True
+    else:
+        return False
+
+def ext_create(cursor, ext):
+    if not ext_exists(cursor, ext):
+        query = 'CREATE EXTENSION "%s"' % ext
+        cursor.execute(query)
+        return True
+    else:
+        return False
+
+# ===========================================
+# Module execution.
+#
+
+def main():
+    module = AnsibleModule(
+        argument_spec=dict(
+            login_user=dict(default="postgres"),
+            login_password=dict(default=""),
+            login_host=dict(default=""),
+            port=dict(default="5432"),
+            db=dict(required=True),
+            ext=dict(required=True, aliases=['name']),
+            state=dict(default="present", choices=["absent", "present"]),
+        ),
+        supports_check_mode = True
+    )
+
+    if not postgresqldb_found:
+        module.fail_json(msg="the python psycopg2 module is required")
+
+    db = module.params["db"]
+    ext = module.params["ext"]
+    port = module.params["port"]
+    state = module.params["state"]
+    changed = False
+
+    # To use defaults values, keyword arguments must be absent, so 
+    # check which values are empty and don't include in the **kw
+    # dictionary
+    params_map = {
+        "login_host":"host",
+        "login_user":"user",
+        "login_password":"password",
+        "port":"port"
+    }
+    kw = dict( (params_map[k], v) for (k, v) in module.params.iteritems() 
+              if k in params_map and v != '' )
+    try:
+        db_connection = psycopg2.connect(database=db, **kw)
+        # Enable autocommit so we can create databases
+        if psycopg2.__version__ >= '2.4.2':
+            db_connection.autocommit = True
+        else:
+            db_connection.set_isolation_level(psycopg2
+                                              .extensions
+                                              .ISOLATION_LEVEL_AUTOCOMMIT)
+        cursor = db_connection.cursor(
+                cursor_factory=psycopg2.extras.DictCursor)
+    except Exception, e:
+        module.fail_json(msg="unable to connect to database: %s" % e)
+
+    try:
+        if module.check_mode:
+            if state == "absent":
+                changed = not db_exists(cursor, ext)
+            elif state == "present":
+                changed = db_exists(cursor, ext)
+            module.exit_json(changed=changed,ext=ext)
+
+        if state == "absent":
+            changed = ext_delete(cursor, ext)
+
+        elif state == "present":
+            changed = ext_create(cursor, ext)
+    except NotSupportedError, e:
+        module.fail_json(msg=str(e))
+    except Exception, e:
+        module.fail_json(msg="Database query failed: %s" % e)
+
+    module.exit_json(changed=changed, db=db)
+
+# import module snippets
+from ansible.module_utils.basic import *
+main()
+