Upgrade to coverage 3.7.1 and have it auto-build itself on first use.

scripts/slave/unittests/test_env.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Script to setup the environment to run unit tests.
 
 Modifies PYTHONPATH to automatically include parent, common and pylibs
 directories.
 """
 
 import os
 import sys
+import textwrap
 
 RUNTESTS_DIR = os.path.dirname(os.path.abspath(__file__))
 DATA_PATH = os.path.join(RUNTESTS_DIR, 'data')
 BASE_DIR = os.path.abspath(os.path.join(RUNTESTS_DIR, '..', '..', '..'))
 
 sys.path.insert(0, os.path.join(BASE_DIR, 'scripts'))
 sys.path.insert(0, os.path.join(BASE_DIR, 'site_config'))
 sys.path.insert(0, os.path.join(BASE_DIR, 'third_party'))
 sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'buildbot_slave_8_4'))
 sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'twisted_10_2'))
 sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'mock-1.0.1'))
 
-try:
-  # The C-compiled coverage engine is WAY faster than the pure python version.
-  # If we have it, then don't bother with the pure python one.
-  import coverage
-except ImportError:
-  sys.path.insert(0, os.path.join(BASE_DIR, 'third_party', 'coverage-3.6'))
-  import coverage
+def ensure_coverage_importable():
+  try:
+    from distutils.version import StrictVersion
+    import coverage
+    if (StrictVersion(coverage.__version__) < StrictVersion('3.7') or
+        not coverage.collector.CTracer):
+      del sys.modules['coverage']
+      del coverage
+    else:
+      return
+  except ImportError:
+    if sys.platform.startswith('win'):
+      print textwrap.dedent("""
+      Please install coverage by running the appropriate installer from:
+        https://pypi.python.org/pypi/coverage/3.7.1
+      """)
+      sys.exit(1)
 
-def print_coverage_warning():
-  if not hasattr(coverage.collector, 'CTracer'):
-    print "WARNING: Using the pure-python coverage module."
-    print "         Install the native python coverage module to speed recipe"
-    print "         training up by an order of magnitude."
-    print
-    print "           pip install coverage"
-    print "         OR"
-    print "           easy_install coverage"
+  try:
+    import setuptools  # pylint: disable=W0612
+  except ImportError:
+    print textwrap.dedent("""
+    No compatible system-wide python-coverage package installed, and
+    setuptools is not installed either. Please obtain setuptools by:
+
+    Debian/Ubuntu:
+      sudo apt-get install python-setuptools python-dev
+
+    OS X:
+      https://pypi.python.org/pypi/setuptools#unix-including-mac-os-x-curl
+
+    Other:
+      https://pypi.python.org/pypi/setuptools#installation-instructions
+    """)
+    sys.exit(1)
+
+  from pkg_resources import get_build_platform
+  try:
+    # Python 2.7 or >= 3.2
+    from sysconfig import get_python_version
+  except ImportError:
+    from distutils.sysconfig import get_python_version
+
+  cov_dir = os.path.join(BASE_DIR, 'third_party', 'coverage-3.7.1')
+  cov_egg = os.path.join(cov_dir, 'dist', 'coverage-3.7.1-py%s-%s.egg' % (
+      get_python_version(), get_build_platform()))
+
+  # The C-compiled coverage engine is WAY faster (and less buggy) than the pure
+  # python version, so we build the dist_egg if necessary.
+  if not os.path.exists(cov_egg):
+    import subprocess
+    print 'Building Coverage 3.7.1'
+    p = subprocess.Popen([sys.executable, 'setup.py', 'bdist_egg'], cwd=cov_dir,
+                         stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    stdout, stderr = p.communicate()
+    if p.returncode != 0:
+      print 'Error while building :('
+      print stdout
+      print stderr
+      if sys.platform.startswith('linux'):
+        print textwrap.dedent("""
+        You probably don't have the 'python-dev' package installed. Install
+        it by running:
+          sudo apt-get install python-dev
+        """)
+      else:
+        print textwrap.dedent("""
+        I'm not sure what's wrong, but your system seems incapable of building
+        python extensions. Please fix that by installing a Python with headers
+        and the approprite command-line build tools for your platform.
+        """)
+      sys.exit(1)
+
+  sys.path.insert(0, cov_egg)
+
+ensure_coverage_importable()
 
 from common import find_depot_tools  # pylint: disable=W0611