Use PATH to lookup test binaries

Instead of hard-coded paths /usr/bin and /usr/sbin, the SlapdObject test
helper now uses PATH env var to find test binaries. For slapd server
binary, sbin paths are automatically added to lookup PATH in case they
are missing.

Signed-off-by: Christian Heimes <cheimes@redhat.com>

Lib/slapdtest/_slapdtest.py

@@ -9,6 +9,7 @@
 
 import os
 import socket
+import sys
 import time
 import subprocess
 import logging
@@ -109,6 +110,46 @@ def requires_ldapi():
         return identity
 
 
+def _which(cmd):
+    """Specialized which command based on shutil.which() from Python 3.6.
+
+    * simplified
+    * always adds /sbin directories to path
+    """
+
+    def _access_check(fn):
+        return (os.path.exists(fn) and os.access(fn, os.F_OK | os.X_OK)
+                and not os.path.isdir(fn))
+
+    # Path with directory part skips PATH lookup.
+    if os.path.dirname(cmd):
+        if _access_check(cmd):
+            return cmd
+        return None
+
+    path = os.environ.get("PATH", os.defpath).split(os.pathsep)
+
+    if sys.platform == 'win32':
+        if os.curdir not in path:
+            path.insert(0, os.curdir)
+        # include path extension (.exe)
+        pathext = os.environ.get("PATHEXT", "").split(os.pathsep)
+        files = [cmd + ext for ext in pathext]
+    else:
+        # always include sbin for slapd binary
+        for sbin in ['/usr/local/sbin', '/sbin', '/usr/sbin']:
+            if sbin not in path:
+                path.append(sbin)
+        files = [cmd]
+
+    for directory in path:
+        for name in files:
+            name = os.path.join(directory, name)
+            if _access_check(name):
+                return name
+    return None
+
+
 def combined_logger(
         log_name,
         log_level=logging.WARN,
@@ -172,8 +213,6 @@ class SlapdObject(object):
     )
 
     TMPDIR = os.environ.get('TMP', os.getcwd())
-    SBINDIR = os.environ.get('SBIN', '/usr/sbin')
-    BINDIR = os.environ.get('BIN', '/usr/bin')
     if 'SCHEMA' in os.environ:
         SCHEMADIR = os.environ['SCHEMA']
     elif os.path.isdir("/etc/openldap/schema"):
@@ -182,12 +221,14 @@ class SlapdObject(object):
         SCHEMADIR = "/etc/ldap/schema"
     else:
         SCHEMADIR = None
-    PATH_LDAPADD = os.path.join(BINDIR, 'ldapadd')
-    PATH_LDAPDELETE = os.path.join(BINDIR, 'ldapdelete')
-    PATH_LDAPMODIFY = os.path.join(BINDIR, 'ldapmodify')
-    PATH_LDAPWHOAMI = os.path.join(BINDIR, 'ldapwhoami')
-    PATH_SLAPD = os.environ.get('SLAPD', os.path.join(SBINDIR, 'slapd'))
-    PATH_SLAPTEST = os.path.join(SBINDIR, 'slaptest')
+    # _check_requirements turns paths into absolute paths
+    PATH_LDAPADD = 'ldapadd'
+    PATH_LDAPDELETE = 'ldapdelete'
+    PATH_LDAPMODIFY = 'ldapmodify'
+    PATH_LDAPWHOAMI = 'ldapwhoami'
+    # The following two binaries are usually in /usr/sbin.
+    PATH_SLAPD = os.environ.get('SLAPD', 'slapd')
+    PATH_SLAPTEST = 'slaptest'
 
     # time in secs to wait before trying to access slapd via LDAP (again)
     _start_sleep = 1.5
@@ -223,13 +264,19 @@ def __init__(self):
         self.clientkey = os.path.join(HERE, 'certs/client.key')
 
     def _check_requirements(self):
-        binaries = [
-            self.PATH_LDAPADD, self.PATH_LDAPMODIFY, self.PATH_LDAPWHOAMI,
-            self.PATH_SLAPD, self.PATH_SLAPTEST
+        names = [
+            "PATH_LDAPADD", "PATH_LDAPMODIFY", "PATH_LDAPDELETE",
+            "PATH_LDAPWHOAMI", "PATH_SLAPD", "PATH_SLAPTEST",
         ]
-        for binary in binaries:
-            if not os.path.isfile(binary):
-                raise ValueError('Binary {} is missing.'.format(binary))
+        for name in names:
+            value = getattr(self, name)
+            binary = _which(value)
+            if binary is None:
+                raise ValueError(
+                    "Command '{}' not found in PATH".format(value)
+                )
+            else:
+                setattr(self, name, binary)
         if self.SCHEMADIR is None:
             raise ValueError('SCHEMADIR is None, ldap schemas are missing.')
 
@@ -359,7 +406,7 @@ def _start_slapd(self):
             self.PATH_SLAPD,
             '-f', self._slapd_conf,
             '-F', self.testrundir,
-            '-h', '%s' % ' '.join(urls),
+            '-h', ' '.join(urls),
         ]
         if self._log.isEnabledFor(logging.DEBUG):
             slapd_args.extend(['-d', '-1'])