[Environment] Use standard python paths (#379)

* Migrate to standard python modules installation paths.

* Remove deprecated fix to import python lib on linux

Plugin/src/SofaPython3/PythonEnvironment.cpp

@@ -180,16 +180,6 @@ void PythonEnvironment::Init()
         SceneLoaderFactory::getInstance()->addEntry(new SceneLoaderPY3());
     }
 
-#if defined(__linux__)
-    // WARNING: workaround to be able to import python libraries on linux (like
-    // numpy), at least on Ubuntu (see http://bugs.python.org/issue4434). It is
-    // not fixing the real problem, but at least it is working for now.
-    // dmarchal: The problem still exists python3 10/10/2018.
-    std::string pythonLibraryName = "libpython" + std::string(pythonVersion,0,3) + "m.so";
-    dlopen( pythonLibraryName.c_str(), RTLD_LAZY|RTLD_GLOBAL );
-    msg_info("SofaPython3") << "Shared library name is '" << pythonLibraryName << "'" ;
-#endif
-
     /// Prevent the python terminal from being buffered, not to miss or mix up traces.
     if( putenv( (char*)"PYTHONUNBUFFERED=1" ) )
         msg_warning("SofaPython3") << "failed to set environment variable PYTHONUNBUFFERED";
@@ -386,10 +376,19 @@ void PythonEnvironment::addPythonModulePathsFromDirectory(const std::string& dir
         return;
     }
 
+    // Using python<MAJOR>.<MINOR> directory suffix for modules paths is now the recommanded
+    // standard location: https://docs.python.org/3.11/install/#how-installation-works and
+    // https://docs.python.org/3.11/library/site.html#module-site 
+    const auto pythonVersionFull = std::string{Py_GetVersion()};
+    const auto pythonVersion = pythonVersionFull.substr(0, pythonVersionFull.find(" ")); // contains major.minor.patch
+    const auto pythonVersionMajorMinor = pythonVersion.substr(0, pythonVersion.rfind(".")); // contains only manjor.minor
+    const auto pythonMajorMinorSuffix = "/python" + pythonVersionMajorMinor;
+
     std::vector<std::string> searchDirs = {
         directory,
         directory + "/lib",
-        directory + "/python3"
+        directory + pythonMajorMinorSuffix,
+        directory + "/python3" // deprecated
     };
 
     // Iterate in the pluginsDirectory and add each sub directory with a 'python' name
@@ -401,7 +400,18 @@ void PythonEnvironment::addPythonModulePathsFromDirectory(const std::string& dir
         const std::string subdir = directory + "/" + *i;
         if (FileSystem::exists(subdir) && FileSystem::isDirectory(subdir))
         {
-            searchDirs.push_back(subdir + "/python3");
+            const std::vector<std::string> suffixes = {
+              pythonMajorMinorSuffix,
+              "/python3" // deprecated
+            };
+            for (const auto& suffix : suffixes)
+            {
+              const auto pythonSubdir = subdir + suffix;
+              if (FileSystem::exists(pythonSubdir) && FileSystem::isDirectory(pythonSubdir))
+              {
+                searchDirs.push_back(pythonSubdir);
+              }
+            }
         }
     }