[lldb/pexpect] Force-set the TERM environment variable

In some environments (typically, buildbots), this variable may not be
available. This can cause tests to behave differently.

Explicitly set the variable to "vt100" to ensure consistent test
behavior. It should not matter that we do not inherit the process TERM
variable, as the child process runs in a new virtual terminal anyway.

lldb/packages/Python/lldbsuite/test/lldbpexpect.py

@@ -1,6 +1,7 @@
 from __future__ import absolute_import
 
 # System modules
+import os
 import sys
 
 # Third-party modules
@@ -29,6 +30,7 @@ else:
         def launch(self, executable=None, extra_args=None, timeout=30, dimensions=None):
             logfile = getattr(sys.stdout, 'buffer',
                               sys.stdout) if self.TraceOn() else None
+
             args = ['--no-lldbinit', '--no-use-colors']
             for cmd in self.setUpCommands():
                 args += ['-O', cmd]
@@ -36,9 +38,13 @@ else:
                 args += ['--file', executable]
             if extra_args is not None:
                 args.extend(extra_args)
+
+            env = dict(os.environ)
+            env["TERM"]="vt100"
+
             self.child = pexpect.spawn(
                     lldbtest_config.lldbExec, args=args, logfile=logfile,
-                    timeout=timeout, dimensions=dimensions)
+                    timeout=timeout, dimensions=dimensions, env=env)
             self.expect_prompt()
             for cmd in self.setUpCommands():
                 self.child.expect_exact(cmd)