Use a lightweight core library (#2212)

* Use poetry-core

* Upgrade dependencies

* No longer use Poetry as a build backend but poetry-core instead

* Use the latest version of poetry-core

Author: sdispater

docs/docs/faq.md

@@ -42,8 +42,8 @@ So, in your `pyproject.toml` file, add this section if it does not already exist
 
 ```toml
 [build-system]
-requires = ["poetry>=0.12"]
-build-backend = "poetry.masonry.api"
+requires = ["poetry-core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"
 ```
 
 And use a `tox.ini` configuration file similar to this:

docs/docs/pyproject.md

@@ -274,16 +274,22 @@ If you publish you package on PyPI, they will appear in the `Project Links` sect
 [PEP-517](https://www.python.org/dev/peps/pep-0517/) introduces a standard way
 to define alternative build systems to build a Python project.
 
-Poetry is compliant with PEP-517 so if you use Poetry to manage your Python
-project you should reference it in the `build-system` section of the `pyproject.toml`
-file like so:
+Poetry is compliant with PEP-517, by providing a lightweight core library,
+so if you use Poetry to manage your Python project you should reference
+it in the `build-system` section of the `pyproject.toml` file like so:
 
 ```toml
 [build-system]
-requires = ["poetry>=0.12"]
-build-backend = "poetry.masonry.api"
+requires = ["poetry_core>=1.0.0"]
+build-backend = "poetry.core.masonry.api"
 ```
 
 !!!note
 
     When using the `new` or `init` command this section will be automatically added.
+
+
+!!!note
+
+    If your `pyproject.toml` file still references `poetry` directly as a build backend,
+    you should update it to reference `poetry_core` instead.

get-poetry.py

@@ -204,8 +204,13 @@ def expanduser(path):
 import os
 
 lib = os.path.normpath(os.path.join(os.path.realpath(__file__), "../..", "lib"))
+vendors = os.path.join(lib, "poetry", "_vendor")
+current_vendors = os.path.join(
+    vendors, "py{}".format(".".join(str(v) for v in sys.version_info[:2]))
+)
 
 sys.path.insert(0, lib)
+sys.path.insert(0, current_vendors)
 
 if __name__ == "__main__":
     from poetry.console import main