Pin poetry deps to work around cryptography requiring Rust issue

pyproject.toml

@@ -11,6 +11,7 @@ include = ["readme.md", "LICENSE.txt"]
 
 [tool.poetry.dependencies]
 python = "~3.6"
+cryptography = "2.7"
 pillar = {path = "../pillar"}
 svn = "~0.3"
 
@@ -20,5 +21,5 @@ mkdocs = "~1.0"
 mkdocs-material = "~4.2"
 
 [build-system]
-requires = ["poetry>=0.12"]
+requires = ["poetry==1.0","cryptography==2.7","setuptools==51.0.0","wheel==0.35.1"]
 build-backend = "poetry.masonry.api"