Cleanup docker before 2.3.0b1 release scripts/Docker/Dockerfile Document/implement pip_sdist source mode for testing the source distribution. Change from multiple if's to case statement. Disable verbose tracing of shells script. Use --build-arg="VERBOSE=1" to enable set -xv. scripts/Docker/roundup_start Report error if demo mode is used with 2.2.0. This catches the easiest case where build is done using pypi before 2.3.0 final is released. Indent demo mode PORT_8080 doc block so it's not lost in a wall of text. doc/installation.txt Document all source --build-args including how to build from pypi using a version specifier. Break out other uses of --build-arg into code blocks. Reference docker compose section rather than referencing docker-compose.yml. Clarify docker hub tagging for devel releases. Minor formatting fixes.

import operator

class MultiMapping:
    def __init__(self, *stores):
        self.stores = list(stores)
    def __getitem__(self, key):
        for store in self.stores:
            if key in store:
                return store[key]
        raise KeyError(key)
    _marker = []
    def get(self, key, default=_marker):
        for store in self.stores:
            if key in store:
                return store[key]
        if default is self._marker:
            raise KeyError(key)
        return default
    def __len__(self):
        return sum([len(x) for x in self.stores])
    def push(self, store):
        self.stores.append(store)
    def pop(self):
        return self.stores.pop()
    def items(self):
        l = []
        for store in self.stores:
            l = l + list(store.items())
        return l