test(nodeenv): make the git-bash probe report why it failed

The first CI run of the new job failed with a bare exit 1 and no
diagnostic: the probe ran through `bash -c` with the script and the
environment path as arguments, so the quoting rules of two command line
parsers sat between the test and what the shell ran, and stderr was not
captured at all. It now writes the probe to a file, traces it with
`set -x` and puts both streams into the assertion message.

The direct call guard matches on $0, which a shell reports in the form
it was given; the test was passing the native `C:\...` path, which no
posix shell would produce.

Author: ekalinin

tests/nodeenv_test.py

@@ -104,18 +104,29 @@ def test_smoke_git_bash(tmpdir):
         '-m', 'nodeenv', '--prebuilt', nenv_path,
     ])
 
-    # node.exe and npm report native paths, so both answers can be
-    # compared with the environment directory as python knows it
-    script = (
-        'set -e\n'
-        'env_dir="$(cygpath "$1")"\n'
-        '. "$env_dir/Scripts/activate"\n'
+    # bash reads the script from a file: passing it inline would put the
+    # quoting rules of two command line parsers between the test and what
+    # the shell ends up running.  `set -x` sends a trace to stderr, which
+    # is only reported when the probe fails.
+    # node.exe and npm answer with native paths, so both can be compared
+    # with the environment directory as python knows it.
+    probe = tmpdir.join('probe.sh')
+    probe.write(
+        'set -ex\n'
+        '. "%s/Scripts/activate"\n'
         'node -p "process.execPath"\n'
-        'npm root -g\n'
+        'npm root -g\n' % nenv_path.replace(os.sep, '/')
     )
-    out = subprocess.check_output(['bash', '-c', script, 'bash', nenv_path])
-    node_exe, npm_root = out.decode('utf-8').splitlines()
-
+    proc = subprocess.run(
+        ['bash', probe.strpath.replace(os.sep, '/')],
+        stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    report = 'exit %s\n--- stdout ---\n%s\n--- stderr ---\n%s' % (
+        proc.returncode,
+        proc.stdout.decode('utf-8', 'replace'),
+        proc.stderr.decode('utf-8', 'replace'))
+
+    assert proc.returncode == 0, report
+    node_exe, npm_root = proc.stdout.decode('utf-8').splitlines()[-2:]
     assert _inside(node_exe, nenv_path), \
         'node resolved to %s, outside %s' % (node_exe, nenv_path)
     # npm would answer with a path outside the environment if activate

tests/test_install_activate.py

@@ -496,7 +496,9 @@ def test_win_activate_is_valid_sh(tmpdir, fake_win):
 
 
 def test_win_activate_refuses_to_be_run_directly(tmpdir, fake_win):
-    activate = str(_install_win(tmpdir).join('activate'))
+    # the guard matches on $0, and a shell reports the path it was given:
+    # from a posix shell on Windows that is the forward slash form
+    activate = str(_install_win(tmpdir).join('activate')).replace(os.sep, '/')
 
     proc = subprocess.Popen(
         ['sh', activate], stdout=subprocess.PIPE, stderr=subprocess.STDOUT)