Put a copy of the wptrunner harness in-tree.

This is the same configuration as gecko and is convenient for making changes compared
to using releases from pypi

tests/wpt/harness/wptrunner/hosts.py

@@ -0,0 +1,104 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import unicode_literals
+
+
+class HostsLine(object):
+    def __init__(self, ip_address, canonical_hostname, aliases=None, comment=None):
+        self.ip_address = ip_address
+        self.canonical_hostname = canonical_hostname
+        self.aliases = aliases if aliases is not None else []
+        self.comment = comment
+        if self.ip_address is None:
+            assert self.canonical_hostname is None
+            assert not self.aliases
+            assert self.comment is not None
+
+    @classmethod
+    def from_string(cls, line):
+        if not line.strip():
+            return
+
+        line = line.strip()
+
+        ip_address = None
+        canonical_hostname = None
+        aliases = []
+        comment = None
+
+        comment_parts = line.split("#", 1)
+        if len(comment_parts) > 1:
+            comment = comment_parts[1]
+
+        data = comment_parts[0].strip()
+
+        if data:
+            fields = data.split()
+            if len(fields) < 2:
+                raise ValueError("Invalid hosts line")
+
+            ip_address = fields[0]
+            canonical_hostname = fields[1]
+            aliases = fields[2:]
+
+        return cls(ip_address, canonical_hostname, aliases, comment)
+
+
+class HostsFile(object):
+    def __init__(self):
+        self.data = []
+        self.by_hostname = {}
+
+    def set_host(self, host):
+        if host.canonical_hostname is None:
+            self.data.append(host)
+        elif host.canonical_hostname in self.by_hostname:
+            old_host = self.by_hostname[host.canonical_hostname]
+            old_host.ip_address = host.ip_address
+            old_host.aliases = host.aliases
+            old_host.comment = host.comment
+        else:
+            self.data.append(host)
+            self.by_hostname[host.canonical_hostname] = host
+
+    @classmethod
+    def from_file(cls, f):
+        rv = cls()
+        for line in f:
+            host = HostsLine.from_string(line)
+            if host is not None:
+                rv.set_host(host)
+        return rv
+
+    def to_string(self):
+        field_widths = [0, 0]
+        for line in self.data:
+            if line.ip_address is not None:
+                field_widths[0] = max(field_widths[0], len(line.ip_address))
+                field_widths[1] = max(field_widths[1], len(line.canonical_hostname))
+
+        lines = []
+
+        for host in self.data:
+            line = ""
+            if host.ip_address is not None:
+                ip_string = host.ip_address.ljust(field_widths[0])
+                hostname_str = host.canonical_hostname
+                if host.aliases:
+                    hostname_str = "%s %s" % (hostname_str.ljust(field_widths[1]),
+                                              " ".join(host.aliases))
+                line = "%s %s" % (ip_string, hostname_str)
+            if host.comment:
+                if line:
+                    line += " "
+                line += "#%s" % host.comment
+            lines.append(line)
+
+        lines.append("")
+
+        return "\n".join(lines)
+
+    def to_file(self, f):
+        f.write(self.to_string().encode("utf8"))