Improve to pip freeze call in InstalledRepository

poetry/repositories/installed_repository.py

@@ -16,7 +16,7 @@ class InstalledRepository(Repository):
         """
         """
         repo = cls()
         repo = cls()
 
 
-        freeze_output = env.run("pip", "freeze")
+        freeze_output = env.run("python", "-m", "pip", "freeze")
         for line in freeze_output.split("\n"):
         for line in freeze_output.split("\n"):
             if "==" in line:
             if "==" in line:
                 name, version = re.split("={2,3}", line)
                 name, version = re.split("={2,3}", line)

tests/repositories/test_installed_repository.py

@@ -10,10 +10,10 @@ orator===0.9.8
 
 
 class MockEnv(BaseMockEnv):
 class MockEnv(BaseMockEnv):
     def run(self, bin, *args):
     def run(self, bin, *args):
-        if bin == "pip" and args[0] == "freeze":
+        if bin == "python" and args[:3] == ("-m", "pip", "freeze"):
             return FREEZE_RESULTS
             return FREEZE_RESULTS
 
 
-        super(MockEnv, self).run(bin, *args)
+        return super(MockEnv, self).run(bin, *args)
 
 
 
 
 def test_load():
 def test_load():