completions/setup: Require prompt_toolkit <2

Turns out that there are a couple of other (non-fatal) breaking changes
in ptk 2 that limit the usefulness of the shell, so we just require v1 now.

elektronn2/utils/ptk_completions.py

@@ -47,10 +47,12 @@
 
 import jedi
 from prompt_toolkit.completion import Completer, Completion
-try:  # prompt_toolkit 2.*
-    from prompt_toolkit.completion import PathCompleter
-except ImportError:  # prompt_toolkit 1.*
+try:
     from prompt_toolkit.contrib.completers import PathCompleter
+except ImportError as e:  # prompt_toolkit 2.*
+    print('\n\n\nprompt_toolkit 2 is not supported. Please downgrade to prompt_toolkit<2.\n\n\n')
+    raise e
+
 from prompt_toolkit.contrib.regular_languages.compiler import \
     compile as compile_grammar
 from prompt_toolkit.contrib.regular_languages.completion import \

requirements.txt

@@ -11,7 +11,7 @@ numba>=0.25
 colorlog>=2.7
 pydotplus
 seaborn
-prompt_toolkit>=1.0.3
+prompt_toolkit>=1.0.3,<2
 jedi>=0.9.0
 psutil>=5.0.1
 

setup.py

@@ -54,7 +54,7 @@ def read(fname):
         'future>=0.15',
         'tqdm>=4.5',
         'colorlog>=2.7',
-        'prompt_toolkit>=1.0.3',
+        'prompt_toolkit>=1.0.3,<2',
         'jedi>=0.9.0',
         'pydotplus',
         'seaborn',