Add SERVER_ENV_CONFIG to configure vars from env. variable

server_environment/README.rst

@@ -47,8 +47,12 @@ You should then edit the settings you need in the
   `default/` directory using the .ini file syntax;
 * each environment you need to define is stored in its own directory
   and can override or extend default values;
-* finally, you can override or extend values in the main configuration
-  file of you instance.
+* you can override or extend values in the main configuration
+  file of you instance;
+* additional configuration can be passed in the environment variable
+  ``SERVER_ENV_CONFIG``, overriding any values set in the configuration files.
+  This is a multi-line environment variable in the same configparser format than
+  the files.
 
 Values associated to keys
 containing 'passw' are only displayed in the 'dev' environment.

server_environment/serv_config.py

@@ -97,9 +97,20 @@ def _load_config():
         config_p.read(conf_files)
     except Exception as e:
         raise Exception('Cannot read config files "%s":  %s' % (conf_files, e))
+
     config_p.read(system_base_config.rcfile)
     config_p.remove_section('options')
 
+    env_config = os.getenv('SERVER_ENV_CONFIG')
+    if env_config:
+        try:
+            config_p.read_string(env_config)
+        except configparser.Error as err:
+            raise Exception(
+                'SERVER_ENV_CONFIG content could not be parsed: %s'
+                % (err,)
+            )
+
     return config_p