When downloading https resources with a self-signed certificate, handle python 2.7.9's API breakage

See #1402579 (Can't install calibre due "ssl.SSLError: [SSL] PEM lib (_ssl.c:2525)")

setup/linux-installer.py

@@ -19,6 +19,7 @@ py3 = sys.version_info[0] > 2
 enc = getattr(sys.stdout, 'encoding', 'UTF-8') or 'utf-8'
 calibre_version = signature = None
 urllib = __import__('urllib.request' if py3 else 'urllib', fromlist=1)
+has_ssl_verify = sys.version_info[:3] >= (2, 7, 9)
 
 if py3:
     unicode = str
@@ -467,7 +468,7 @@ def match_hostname(cert, hostname):
         raise CertificateError("no appropriate commonName or "
             "subjectAltName fields were found")
 
-if py3:
+if has_ssl_verify:
     class HTTPSConnection(httplib.HTTPSConnection):
 
         def __init__(self, ssl_version, *args, **kwargs):

src/calibre/utils/https.py

@@ -6,11 +6,12 @@ from __future__ import (unicode_literals, division, absolute_import,
 __license__ = 'GPL v3'
 __copyright__ = '2014, Kovid Goyal <kovid at kovidgoyal.net>'
 
-import ssl, socket, re
+import ssl, socket, re, sys
 from contextlib import closing
 
 from calibre import get_proxies
 from calibre.constants import ispy3
+has_ssl_verify = sys.version_info[:3] >= (2, 7, 9)
 
 class HTTPError(ValueError):
 
@@ -24,6 +25,11 @@ class HTTPError(ValueError):
 if ispy3:
     from urllib.parse import urlparse
     import http.client as httplib
+else:
+    import httplib
+    from urlparse import urlsplit as urlparse
+
+if has_ssl_verify:
     class HTTPSConnection(httplib.HTTPSConnection):
 
         def __init__(self, ssl_version, *args, **kwargs):
@@ -33,9 +39,6 @@ if ispy3:
             context.verify_mode = ssl.CERT_REQUIRED
             httplib.HTTPSConnection.__init__(self, *args, **kwargs)
 else:
-    import httplib
-    from urlparse import urlsplit as urlparse
-
     # Check certificate hostname {{{
     # Implementation taken from python 3
     class CertificateError(ValueError):