Fix create_pipfile version parsing

Signed-off-by: Dan Ryan <dan@danryan.co>

pipenv/project.py

@@ -44,6 +44,7 @@ from .environments import (
     PIPENV_VIRTUALENV,
     PIPENV_TEST_INDEX,
     PIPENV_PYTHON,
+    PIPENV_DEFAULT_PYTHON_VERSION,
 )
 
 
@@ -578,12 +579,17 @@ class Project(object):
             u'dev-packages': {},
         }
         # Default requires.
-        required_python = python or self.which(
-            'python', self.virtualenv_location
-        )
-        data[u'requires'] = {
-            'python_version': python_version(required_python)[: len('2.7')]
-        }
+        required_python = python
+        if not python:
+            if self.virtualenv_location:
+                required_python = self.which('python', self.virtualenv_location)
+            else:
+                required_python = self.which('python')
+        version = python_version(required_python) or PIPENV_DEFAULT_PYTHON_VERSION
+        if version and len(version) >= 3:
+            data[u'requires'] = {
+                'python_version': version[: len('2.7')]
+            }
         self.write_toml(data, 'Pipfile')
 
     def write_toml(self, data, path=None):

pipenv/utils.py

@@ -220,12 +220,13 @@ def python_version(path_to_python):
         c = delegator.run([path_to_python, '--version'], block=False)
     except Exception:
         return None
-    if c.return_code != 0:
-        return None
+    c.block()
     version = parse_python_version(c.out.strip() or c.err.strip())
-    if not version:
+    try:
+        version = u'{major}.{minor}.{micro}'.format(**version)
+    except TypeError:
         return None
-    return u'{major}.{minor}.{micro}'.format(**version)
+    return version
 
 
 def escape_grouped_arguments(s):