Fix an error when locking dependencies on Python 2.7

CHANGELOG.md

 # Change Log
 
+## [Unreleased]
+
+### Fixed
+
+- Fixed an error when locking dependencies on Python 2.7.
+
+
 ## [0.11.0] - 2018-06-28
 
 ### Added

poetry/packages/locker.py

@@ -144,13 +144,12 @@ class Locker:
         # packages first and metadata after
         with self._lock.open("w", encoding="utf-8") as f:
             f.write(self._lock.dumps({"package": data["package"]}, sort=True))
-            f.write("\n")
+            f.write(u"\n")
             if "extras" in data:
                 f.write(self._lock.dumps({"extras": data["extras"]}, sort=True))
-                f.write("\n")
+                f.write(u"\n")
 
             f.write(self._lock.dumps({"metadata": data["metadata"]}, sort=True))
-            f.write("\n")
 
         self._lock_data = None
 

tests/packages/test_locker.py

+import pytest
+import tempfile
+
+from poetry.packages.locker import Locker
+from poetry.packages.project_package import ProjectPackage
+
+from ..helpers import get_package
+
+
+@pytest.fixture
+def locker():
+    with tempfile.NamedTemporaryFile() as f:
+        f.close()
+        locker = Locker(f.name, {})
+
+        return locker
+
+
+@pytest.fixture
+def root():
+    return ProjectPackage("root", "1.2.3")
+
+
+def test_lock_file_data_is_ordered(locker, root):
+    package_a = get_package("A", "1.0.0")
+    package_a.add_dependency("B", "^1.0")
+    package_a.hashes = ["456", "123"]
+    packages = [package_a, get_package("B", "1.2")]
+
+    locker.set_lock_data(root, packages)
+
+    with locker.lock.open(encoding="utf-8") as f:
+        content = f.read()
+
+    expected = """[[package]]
+category = "main"
+description = ""
+name = "A"
+optional = false
+platform = "*"
+python-versions = "*"
+version = "1.0.0"
+
+[package.dependencies]
+B = "^1.0"
+
+[[package]]
+category = "main"
+description = ""
+name = "B"
+optional = false
+platform = "*"
+python-versions = "*"
+version = "1.2"
+
+[metadata]
+content-hash = "78ac9903d6fcbe1b1322857731bff3cac904ef8fd5e72c6c768761f28f66b8ea"
+platform = "*"
+python-versions = "*"
+
+[metadata.hashes]
+A = ["123", "456"]
+B = []
+"""
+
+    assert expected == content