Fixed single digit versions not working

Fixes #208.

CHANGES.txt

@@ -1,6 +1,7 @@
 Unreleased
 ==========
 - Fixed displaying of errors on Python 3
+- Fixed single digit versions in wheel files not being properly recognized
 
 0.30.0
 ======

tests/test_install.py

@@ -100,3 +100,9 @@ def get_supported():
 def test_install_tool():
     """Slightly improve coverage of wheel.install"""
     wheel.tool.install([TESTWHEEL], force=True, dry_run=True)
+
+
+def test_wheelfile_re():
+    # Regression test for #208
+    wf = WheelFile('foo-2-py3-none-any.whl')
+    assert wf.distinfo_name == 'foo-2.dist-info'

wheel/install.py

@@ -34,9 +34,8 @@
 # Non-greedy matching of an optional build number may be too clever (more
 # invalid wheel filenames will match). Separate regex for .dist-info?
 WHEEL_INFO_RE = re.compile(
-    r"""^(?P<namever>(?P<name>.+?)(-(?P<ver>\d.+?))?)
-    ((-(?P<build>\d.*?))?-(?P<pyver>.+?)-(?P<abi>.+?)-(?P<plat>.+?)
-    \.whl|\.dist-info)$""",
+    r"""^(?P<namever>(?P<name>.+?)-(?P<ver>\d.*?))(-(?P<build>\d.*?))?
+     -(?P<pyver>[a-z].+?)-(?P<abi>.+?)-(?P<plat>.+?)(\.whl|\.dist-info)$""",
     re.VERBOSE).match