Se corrige el mensaje de error del login

Adicionalmente, se aplica linter al HTML.

Frontend Angular 4/src/app/login/login.component.html

-<div class="login-page" style="background: #004869;">
-    <div class="row">
-        <div class="col-md-4 push-md-4" style="padding: 55px 35px;background: rgba(255,255,255,0.15);border-radius: 8px;">
-            <h1>MateFun</h1>
-            <form role="form">
-                <div class="form-content">
-                    <div class="form-group">
-                        <input type="text" [(ngModel)]=model.cedula  name="cedula" class="form-control input-underline input-lg"  placeholder='{{ "i18n.object.user" | translate | titleCase }}'>
-                    </div>
+<div class="login-page" style="background: #004869">
+  <div class="row">
+    <div
+      class="col-md-4 push-md-4"
+      style="
+        padding: 55px 35px;
+        background: rgba(255, 255, 255, 0.15);
+        border-radius: 8px;
+      "
+    >
+      <h1>MateFun</h1>
+      <form role="form">
+        <div class="form-content">
+          <div class="form-group">
+            <input
+              type="text"
+              [(ngModel)]="model.cedula"
+              name="cedula"
+              class="form-control input-underline input-lg"
+              placeholder="{{ 'i18n.object.user' | translate | titleCase }}"
+            />
+          </div>
 
-                    <div class="form-group">
-                        <input
-                            type="password"
-                            [(ngModel)]=model.password
-                            (keyup.enter)=login()
-                            name="password"
-                            class="form-control input-underline input-lg"
-                            placeholder='{{ "i18n.object.password" | translate | titleCase }}'>
-                    </div>
-                    <!-- <div class="form-group" style="margin-bottom: 0px; text-align: left;">
+          <div class="form-group">
+            <input
+              type="password"
+              [(ngModel)]="model.password"
+              (keyup.enter)="login()"
+              name="password"
+              class="form-control input-underline input-lg"
+              placeholder="{{ 'i18n.object.password' | translate | titleCase }}"
+            />
+          </div>
+          <!-- <div class="form-group" style="margin-bottom: 0px; text-align: left;">
                         <div ngbDropdown class="d-inline-block language-switcher">
                             <button class="btn btn-outline-secondary" id="input-lang" ngbDropdownToggle>
                                 <span class="flag-icon flag-icon-{{model.language.flagCode}}"></span>
@@ -35,22 +49,46 @@
                             </div>
                         </div>
                      </div> -->
-                </div>
+        </div>
 
-                <a class="btn rounded-btn" style="background: transparent;color: white;cursor: pointer;width: 159px;margin-right: 3px;" (click)=login()> {{ "i18n.action.login" | translate | titleCase }} </a>
-                <a class="btn rounded-btn" style="background: transparent;color: white;cursor: pointer;width: 159px;margin-left: 3px;" (click)=invitado()> {{ "i18n.object.guest" | translate | titleCase }} </a>
-                &nbsp;
-                <div class="loading" *ngIf="loading">
-                    <div class="loading-bar"></div>
-                    <div class="loading-bar"></div>
-                    <div class="loading-bar"></div>
-                </div>
-                <div class="login-error" *ngIf="error && !loading">
-                    <ngb-alert [dismissible]="false" [type]="'danger'">
-                        <strong>Error!</strong> {{errorText}}.
-                    </ngb-alert>
-                </div>
-            </form>
+        <a
+          class="btn rounded-btn"
+          style="
+            background: transparent;
+            color: white;
+            cursor: pointer;
+            width: 159px;
+            margin-right: 3px;
+          "
+          (click)="login()"
+        >
+          {{ "i18n.action.login" | translate | titleCase }}
+        </a>
+        <a
+          class="btn rounded-btn"
+          style="
+            background: transparent;
+            color: white;
+            cursor: pointer;
+            width: 159px;
+            margin-left: 3px;
+          "
+          (click)="invitado()"
+        >
+          {{ "i18n.object.guest" | translate | titleCase }}
+        </a>
+        &nbsp;
+        <div class="loading" *ngIf="loading">
+          <div class="loading-bar"></div>
+          <div class="loading-bar"></div>
+          <div class="loading-bar"></div>
+        </div>
+        <div class="login-error" *ngIf="error && !loading">
+          <ngb-alert [dismissible]="false" [type]="'danger'">
+            <strong>¡Error!</strong>{{ errorText }}
+          </ngb-alert>
         </div>
+      </form>
     </div>
+  </div>
 </div>