rust-cpython: drop direct dependency on python(27|3)_sys

We no longer use it.

rust/Cargo.lock

@@ -66,8 +66,6 b' dependencies = ['
  "cpython 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "hg-core 0.1.0",
  "libc 0.2.45 (registry+https://github.com/rust-lang/crates.io-index)",
- "python27-sys 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "python3-sys 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]

rust/hg-cpython/Cargo.toml

@@ -11,12 +11,9 b' crate-type = ["cdylib"]'
 [features]
 default = ["python27"]
 
-python27 = ["cpython/python27-sys",
-            "cpython/extension-module-2-7",
-            "python27-sys",
-            ]
+python27 = ["cpython/python27-sys", "cpython/extension-module-2-7"]
 
-python3 = ["python3-sys", "cpython/python3-sys", "cpython/extension-module"]
+python3 = ["cpython/python3-sys", "cpython/extension-module"]
 
 [dependencies]
 hg-core = { path = "../hg-core" }
@@ -25,11 +22,3 b" libc = '*'"
 [dependencies.cpython]
 version = "0.3"
 default-features = false
-
-[dependencies.python27-sys]
-version = "0.3"
-optional = true
-
-[dependencies.python3-sys]
-version = "0.3"
-optional = true