Added env var checking to all config get methods.

The new method replaces the manual env var parsing with simply setting
the config's value to the env var value. This lets the normal parsing
methods do the work later, to avoid duplication of effort.

buildozer/__init__.py

@@ -915,6 +915,8 @@ class Buildozer(object):
         # get a key as a list of string, seperated from the comma
 
         # if a section:token is defined, let's use the content as a list.
+        set_config_from_env(section, token, self.config)
+
         l_section = '{}:{}'.format(section, token)
         if self.config.has_section(l_section):
             values = self.config.options(l_section)
@@ -936,9 +938,7 @@ class Buildozer(object):
         # monkey-patch method for ConfigParser
         # get an appropriate env var if it exists, else
         # get a key in a section, or the default
-        env_var = query_env(section, token)
+        set_config_from_env(section, token, self.config)
-        if env_var is not None:
-            return env_var
         if not self.config.has_section(section):
             return default
         if not self.config.has_option(section, token):
@@ -948,9 +948,7 @@ class Buildozer(object):
     def _get_config_bool(self, section, token, default=False):
         # monkey-patch method for ConfigParser
         # get a key in a section, or the default
-        env_var = query_env_bool(section, token)
+        set_config_from_env(section, token, self.config)
-        if env_var is not None:
-            return env_var
         if not self.config.has_section(section):
             return default
         if not self.config.has_option(section, token):
@@ -1214,31 +1212,22 @@ def run_remote():
     except BuildozerException as error:
         Buildozer().error('%s' % error)
 
+def set_config_from_env(section, token, config):
+    '''Given a config section and token, checks for an appropriate
+    environment variable. If the variable exists, sets the config entry to
+    its value.
 
-def query_env(section, token):
+    The environment variable checked is of the form SECTION_TOKEN, all
-    '''Given config section and token names, returns the environment
+    upper case, with any dots replaced by underscores.
-    variable SECTION_TOKEN, or None if the variable does not exist.'''
+
+    Returns True if the environment variable exists and was used, or
+    False otherwise.
+
+    '''
     env_var_name = ''.join([section.upper(), '_',
                             token.upper().replace('.', '_')])
     env_var = os.environ.get(env_var_name)
-    return env_var
-
-def query_env_bool(section, token):
-    '''Given config section and token names, uses query_env to query an
-    appropriate environment variable. If the variable exists, coerces to a
-    bool before returning.'''
-    env_var = query_env(section, token)
     if env_var is None:
-        return env_var
-    elif env_var.tolower() in ['1', 'yes', 'true', 'on']:
-        return True
-    elif env_var.tolower() in ['0', 'no', 'false', 'off']:
         return False
-    else:
+    config.set(section, token, env_var)
-        env_var_name = ''.join([section.upper(), '_',
+    return True
-                                token.upper().replace('.', '_')])
-        raise ValueError('Failed to parse {} as a config boolean. Should be one'
-                         'of {}'.format(env_var_name
-                                        ['1', 'yes', 'true', 'on',
-                                         '0', 'no', 'false', 'off']))
-