Problem: multiline strings are a pain to represent (other than of-course in docstrings), representing a multiline string inside a function looks something like this -

def foo():
    # some code
    ...
    ...
    # some code
    text = """abc meta alpha chronos
dudes uptomes this text
is nonsense"""
    return somethingwith(text)

or

def foo():
    # some code
    ...
    ...
    # some code
    text = "\n".join(["abc meta alpha chronos",
                      "dudes uptomes this text",
                      "is nonsense"])
    return somethingwith(text)

an enhancement would be - 

def foo():
    # some code
    ...
    ...
    # some code
    text = i"""
            abc meta alpha chronos
            dudes uptomes this text
            is nonsense
            """
    return somethingwith(text)
i.e. all initial spaces are not considered as a part of the string in each ine

for example while throwing an exception -
def foo(bad_param):
    ...
    try:
        some_function_on(bad_param)
    except someException:
        throw(fi"""
                you cant do that because, and I'm gonna explain
                this in a paragraph of text with this {variable}
                because it explains things more clearly, also
                here is the {bad_param}
                """)
    ...
which is far neater than -

def foo(bad_param):
    ...
    try:
        some_function_on(bad_param)
    except someException:
        throw(f"""you cant do that because, and I'm gonna explain
this in a paragraph of text with this {variable}
because it explains things more clearly, also
here is the {bad_param}""")
    ...

pros:
    - represented code is closer to output text
    - implementation should not be too hard

This type of enhancements should be in the first place discussed on python-ideas mailing list and a PEP would probably be needed at the second stage. Not that I think it's likely this suggestion has much chance.

What you're desiring can already be implemented using implicit string concatenation (with addition of some parentheses in some of your examples).

Some discussions in the past and the common suggestion/idiom is to use textwrap.dedent. I agree with @SilentGhost that it should be first brought up in python-ideas and also addressing the concerns for similar proposal in the past if they are still valid.

Proposes d"" for indentation : https://mail.python.org/pipermail/python-ideas/2010-November/008589.html
https://mail.python.org/pipermail/python-dev/2005-July/054649.html