Move is_package and get_model_package_path to util

spacy/util.py

@@ -2,6 +2,8 @@
 from __future__ import unicode_literals, print_function
 
 import ujson
+import pip
+import importlib
 import regex as re
 from pathlib import Path
 import sys
@@ -106,6 +108,29 @@ def read_json(location):
         return ujson.load(f)
 
 
+def is_package(origin):
+    """
+    Check if string maps to a package installed via pip.
+    """
+    packages = pip.get_installed_distributions()
+    for package in packages:
+        if package.project_name.replace('-', '_') == origin:
+            return True
+    return False
+
+
+
+def get_model_package_path(package_name):
+    # Here we're importing the module just to find it. This is worryingly
+    # indirect, but it's otherwise very difficult to find the package.
+    # Python's installation and import rules are very complicated.
+    pkg = importlib.import_module(package_name)
+    package_path = Path(pkg.__file__).parent.parent
+    meta = parse_package_meta(package_path, package_name)
+    model_name = '%s-%s' % (package_name, meta['version'])
+    return package_path / package_name / model_name
+
+
 def parse_package_meta(package_path, package, require=True):
     """
     Check if a meta.json exists in a package and return its contents as a