diff --git a/python/junit5Tests-framework/src/com/intellij/python/junit5Tests/framework/env/impl/VanillaPythonEnvExtension.kt b/python/junit5Tests-framework/src/com/intellij/python/junit5Tests/framework/env/impl/VanillaPythonEnvExtension.kt
index 1e982f9b5a11..64aa02d895a4 100644
--- a/python/junit5Tests-framework/src/com/intellij/python/junit5Tests/framework/env/impl/VanillaPythonEnvExtension.kt
+++ b/python/junit5Tests-framework/src/com/intellij/python/junit5Tests/framework/env/impl/VanillaPythonEnvExtension.kt
@@ -3,8 +3,10 @@ package com.intellij.python.junit5Tests.framework.env.impl
 
 import com.intellij.execution.configurations.GeneralCommandLine
 import com.intellij.execution.process.CapturingProcessHandler
+import com.intellij.execution.process.ProcessNotCreatedException
 import com.intellij.ide.util.PropertiesComponent
 import com.intellij.python.community.impl.poetry.poetryPath
+import com.intellij.python.community.testFramework.testEnv.PythonType
 import com.intellij.python.community.testFramework.testEnv.TypeVanillaPython3
 import com.intellij.python.junit5Tests.framework.env.PythonBinaryPath
 import com.intellij.python.junit5Tests.framework.resolvePythonTool
@@ -31,7 +33,20 @@ internal class VanillaPythonEnvExtension : PythonEnvExtensionBase<PythonBinary,
   override fun onEnvFound(env: PythonBinary) {
     val poetry = env.resolvePythonHome().resolvePythonTool("poetry")
     if (poetry !in checkedPoetries) {
-      val output = CapturingProcessHandler(GeneralCommandLine(poetry.toString(), "--version")).runProcess(60_000, true)
+      val output = try {
+        CapturingProcessHandler(GeneralCommandLine(poetry.toString(), "--version")).runProcess(60_000, true)
+      }
+      catch (e: ProcessNotCreatedException) {
+        val customPythonMessage = buildString {
+          PythonType.customPythonMessage?.let {
+            append(it)
+            append(" install poetry there, i.e: 'python -m pip install poetry' ")
+          }
+          append(" or run/rerun ")
+          append(PythonType.BUILD_KTS_MESSAGE)
+        }
+        throw AssertionError(customPythonMessage, e)
+      }
       assert(output.exitCode == 0) { "$poetry seems to be broken, output: $output. For Windows check `fix_path.cmd`" }
       LOG.info("Poetry found at $poetry")
       checkedPoetries[poetry] = Unit
diff --git a/python/services/system-python/tests/com/intellij/python/junit5Tests/env/systemPython/impl/EnvTestPythonProvider.kt b/python/services/system-python/tests/com/intellij/python/junit5Tests/env/systemPython/impl/EnvTestPythonProvider.kt
index 22bcb6e050bc..966cb2d76175 100644
--- a/python/services/system-python/tests/com/intellij/python/junit5Tests/env/systemPython/impl/EnvTestPythonProvider.kt
+++ b/python/services/system-python/tests/com/intellij/python/junit5Tests/env/systemPython/impl/EnvTestPythonProvider.kt
@@ -21,6 +21,7 @@ internal class EnvTestPythonProvider : SystemPythonProvider {
     var pythons = emptySet<PythonBinary>()
     if (eelApi == localEel) {
       // Add Py27 temporary to test Py27
+      // It is perfectly valid not to find any python because some tests might run without a python and still have this module on a class-path
       pythons = merge(TypeVanillaPython3.getTestEnvironments(), TypeVanillaPython2.getTestEnvironments())
         .map { (python, closeable) ->
           Disposer.register(ApplicationManager.getApplication()) {
diff --git a/python/setup-test-environment/src/com/intellij/python/community/testFramework/testEnv/PythonType.kt b/python/setup-test-environment/src/com/intellij/python/community/testFramework/testEnv/PythonType.kt
index 2b5300100338..d7fa08decf54 100644
--- a/python/setup-test-environment/src/com/intellij/python/community/testFramework/testEnv/PythonType.kt
+++ b/python/setup-test-environment/src/com/intellij/python/community/testFramework/testEnv/PythonType.kt
@@ -11,21 +11,27 @@ import org.jetbrains.annotations.NonNls
 import java.nio.file.Path
 import java.util.concurrent.ConcurrentHashMap
 import kotlin.Result.Companion.failure
+import kotlin.io.path.exists
+import kotlin.io.path.isDirectory
 
 /**
  * Gradle script installs two types of python: conda and vanilla. Env could be obtained by [createSdkClosableEnv] which also provides closable
  * to clean up after the usage
  */
 abstract class PythonType<T : Any>(private val tag: @NonNls String) {
-  private companion object {
-    val cache: MutableMap<Set<String>, List<Path>> = ConcurrentHashMap()
+  companion object {
+    private val cache: MutableMap<Set<String>, List<Path>> = ConcurrentHashMap()
+    private const val PYTHON_FOR_TESTS: String = "PYTHON_FOR_TESTS"
+    private val customPython: String? get() = System.getenv(PYTHON_FOR_TESTS)
+    val BUILD_KTS_MESSAGE: String = "`build.gradle.kts` from the same module ${PythonType::class} sits in. Be sure to read it first: you will need to run `gradle build` there"
+    val customPythonMessage: String? get() = customPython?.let { "You are using custom python $it set by $PYTHON_FOR_TESTS env var" }
   }
 
   /**
    * Returns all test environments ordered from newest (highest) to oldest: each must be closed after the test.
    * If in doubt, take first
    */
-  suspend fun getTestEnvironments(vararg additionalTags: @NonNls String): Flow<Pair<T, AutoCloseable>> {
+  suspend fun getTestEnvironments(vararg additionalTags: @NonNls String, ensureAtLeastOnePython: Boolean = false): Flow<Pair<T, AutoCloseable>> {
     val key = setOf(*additionalTags)
     val pythons = cache.getOrPut(key) {
       PyEnvTestSettings
@@ -42,9 +48,33 @@ abstract class PythonType<T : Any>(private val tag: @NonNls String) {
         }
         .sortedByDescending { (_, languageLevel) -> languageLevel }
         .map { (path, _) -> path }
+    }.toMutableList()
+    val customPythonDir = if (pythons.isEmpty() && ensureAtLeastOnePython) {
+      val pythonStr = customPython
+      if (pythonStr == null) {
+        error("""
+          To run this test you need a python interpreter. You have two options:
+          
+          1. Use $BUILD_KTS_MESSAGE.
+          2. Set env variable $PYTHON_FOR_TESTS to the executable python file you already have, i.e: `/bin/python3` or `c:\python\python.exe`
+        """.trimIndent())
+      }
+      val pythonPath = Path.of(pythonStr)
+      val pythonBinary = when {
+                           pythonPath.isDirectory() -> VirtualEnvReader.Instance.findPythonInPythonRoot(pythonPath)
+                           pythonPath.exists() -> pythonPath
+                           else -> null
+                         } ?: error("$PYTHON_FOR_TESTS env var points to something that is not a python: $pythonPath")
+      pythonBinary.parent
+    }
+    else {
+      null
+    }
+    if (customPythonDir != null) {
+      pythons.add(customPythonDir)
     }
     return pythons.asFlow()
-      .filter { typeMatchesEnv(it, *additionalTags) }
+      .filter { it == customPythonDir || typeMatchesEnv(it, *additionalTags) }
       .map { envDir ->
         pythonPathToEnvironment(
           VirtualEnvReader.Instance.findPythonInPythonRoot(envDir)
@@ -57,7 +87,7 @@ abstract class PythonType<T : Any>(private val tag: @NonNls String) {
    * Returns sdk, (whatever it means) test environment and closable that must be closed after the test
    */
   suspend fun createSdkClosableEnv(vararg additionalTags: @NonNls String): Result<Triple<Sdk, AutoCloseable, T>> =
-    getTestEnvironments(*additionalTags).firstOrNull()?.let { (env, closable) ->
+    getTestEnvironments(*additionalTags, ensureAtLeastOnePython = true).firstOrNull()?.let { (env, closable) ->
       Result.success(Triple(createSdkFor(env), closable, env))
     }
     ?: failure(AssertionError("No python found. See ${PyEnvTestSettings::class} class for more info"))