Fix copy_extra_sources for remote URLs

Fix #387

A build with a remote URL in its `SourceX` will work only with

    %_disable_source_fetch 0

macro defined. It can be done either globally via `~/.rpmmacros` or by
using tito with following parameter

    --rpmbuild-options="--define '%_disable_source_fetch 0'"

IMHO this macro should be set by default but we should also introduce
a switch to turn it off (like e.g. Mock or Copr do). Since it is not
related to fixing #387, I am not doing it in this commit.

src/tito/builder/main.py

@@ -34,7 +34,7 @@ from tito.common import scl_to_rpm_option, get_latest_tagged_version, \
     find_cheetah_template_file, render_cheetah, replace_spec_release, \
     find_spec_like_file, warn_out, get_commit_timestamp, chdir, mkdir_p, \
     find_git_root, info_out, munge_specfile, BUILDCONFIG_SECTION
-from tito.compat import getstatusoutput, getoutput
+from tito.compat import getstatusoutput, getoutput, urlparse
 from tito.exception import RunCommandException
 from tito.exception import TitoException
 from tito.config_object import ConfigObject
@@ -508,6 +508,15 @@ class Builder(ConfigObject, BuilderBase):
             if os.path.isfile(dst_file):
                 debug('Source file "%s" already exists. Skiping.' % dst_file)
                 continue
+
+            parse = urlparse(source)
+            if parse.scheme and parse.netloc:
+                # If macro `%_disable_source_fetch 0` is defined, the file will
+                # be automatically downloaded by rpmbuild to the SOURCES
+                # directory. We can safely skip it here.
+                debug('Source "%s" is not a local file. Skiping.' % source)
+                continue
+
             src = os.path.join(self.rpmbuild_sourcedir, self.tgz_dir, source)
             if os.path.islink(src) and os.path.isabs(src):
                 src = os.path.join(self.start_dir, os.readlink(src))

src/tito/compat.py

@@ -25,6 +25,7 @@ if PY2:
     from ConfigParser import NoOptionError
     from ConfigParser import RawConfigParser
     from StringIO import StringIO
+    from urlparse import urlparse
     import xmlrpclib
     text_type = unicode
     binary_type = str
@@ -33,6 +34,7 @@ else:
     from configparser import NoOptionError
     from configparser import RawConfigParser
     from io import StringIO
+    from urllib.parse import urlparse
     import xmlrpc.client as xmlrpclib
     text_type = str
     binary_type = bytes